concurring, in which AMBRO, FUENTES and FISHER, Circuit Judges, join.
I agree with Judge Hardiman that Boyd did not procedurally default his claim. “When a state court refuses to readjudicate a claim on the ground that it has been previously determined, the court’s decision does not indicate that the claim has been procedurally defaulted. To the contrary, it provides strong evidence that the claim has already been given full consideration by the state courts and thus is ripe for federal adjudication.” Cone v. Bell, — U.S. -,-, 129 S.Ct. 1769, 1781, 173 L.Ed.2d 701 (2009). Accordingly, I join Part III of Judge Hardiman’s opinion.
In my view, however, Tollett v. Henderson, 411 U.S. 258, 93 S.Ct. 1602, 36 L.Ed.2d 235 (1973), and Mabry v. Johnson, 467 U.S. 504, 104 S.Ct. 2543, 81 L.Ed.2d 437 (1984), do not dispose of this case. Instead, I believe the well-settled test for ineffective assistance of counsel set forth in Strickland v. Washington, 466 U.S. 668, 104 S.Ct. 2052, 80 L.Ed.2d 674 (1984), provides the rule of decision, as the Magistrate Judge and District Court determined. At the same time, however, I believe the District Court erred in reviewing Boyd’s ineffective assistance of counsel claim under a de novo standard. Because the Pennsylvania Superior Court adjudicated Boyd’s claim on the merits, habeas relief is subject to the restrictions imposed by the Antiterrorism and Effective Death Penalty Act of 1996 (AEDPA), 28 U.S.C. § 2254(d). Accordingly, I would reverse and remand with instructions for the District Court to apply the proper AEDPA standards.
AEDPA provides:
An application for a writ of habeas corpus on behalf of a person in custody pursuant to the judgment of a State court shall not be granted with respect to any claim that was adjudicated on the merits in State court proceedings unless the adjudication of the claim—
(1) resulted in a decision that was contrary to, or involved an unreasonable application of, clearly established Federal law, as determined by the Supreme Court of the United States; or
(2) resulted in a decision that was based on an unreasonable determination of the facts in light of the evidence presented in the State court proceeding.
28 U.S.C. § 2254(d). As the Supreme Court has explained, AEDPA “place[d] a new constraint on the power of a federal habeas court to grant a state prisoner’s application for a writ of habeas corpus with respect to claims adjudicated on the merits in state court.” Terry Williams v. Taylor, 529 U.S. 362, 412, 120 S.Ct. 1495, *334146 L.Ed.2d 389 (2000) (majority opinion of O’Connor, J.). Accordingly, as a threshold matter, in order to determine whether the constraints of § 2254(d) apply to federal review of Boyd’s petition, we must determine whether the state courts decided his claim “on the merits.” See Chadwick v. Janecka, 312 F.3d 597, 605-06 (3d Cir. 2002). If the state courts decided a given claim on the merits, “our standard of review is narrow:” we may not grant the writ unless the state-court adjudication of that claim meets one of the conditions set forth in § 2254(d)(1) or (d)(2). Id. at 605. Conversely, “[w]e review de novo issues that the state court did not decide on the merits.” Bond v. Beard, 539 F.3d 256, 263 (3d Cir.2008). The District Court concluded without elaboration that it would “review [Boyd’s petition] de novo as the state courts failed to accurately construe Petitioner’s claim against trial counsel.” Boyd v. Nish, No. 06-0491, 2007 WL 403884, at *2 (E.D.Pa. Jan.31, 2007).2
State-court adjudication “on the merits” has been defined as follows:
A matter is “adjudicated on the merits” if there is a “decision finally resolving the parties’ claims, with res judicata effect, that is based on the substance of the claim advanced, rather than on a procedural, or other, ground.” ... [Section] 2254(d) applies regardless of the procedures employed or the decision reached by the state court, as long as a substantive decision was reached; the adequacy of the procedures and of the decision are addressed through the lens of § 2254(d), not as a threshold matter.
Teti v. Bender, 507 F.3d 50, 56-57 (1st Cir.2007) (quoting Sellan v. Kuhlman, 261 F.3d 303, 311 (2d Cir.2001), and citing cases from the Fourth, Fifth, Sixth, Ninth, Tenth and Eleventh Circuits); accord Thomas v. Horn, 570 F.3d 105, 114-15 (3d Cir.2009); Rompilla v. Horn, 355 F.3d 233, 247-48 (3d Cir.2004), rev’d on other grounds sub nom. Rompilla v. Beard, 545 U.S. 374, 125 S.Ct. 2456, 162 L.Ed.2d 360 (2005). Our precedent “stand[s] for the proposition that, if an examination of the opinions of the state courts shows that they misunderstood the nature of a properly exhausted claim and thus failed to adjudicate that claim on the merits, the deferential standards of review in AEDPA do not apply.” Chadwick, 312 F.3d at 606. But when the state courts have “previously considered and rejected the federal claim on the merits,” the § 2254(d) standards do apply. Siehl v. Grace, 561 F.3d 189, 195 (3d Cir.2009).
Boyd has claimed his trial counsel was ineffective on two different grounds. The first ground, initially presented on direct appeal in Pennsylvania Superior Court, was that trial counsel allegedly failed to give Boyd sufficient advice about the sentencing guidelines to allow him to make an informed decision about whether to accept *335the Commonwealth’s initial plea offer. Boyd does not dispute that the Pennsylvania Superior Court recognized this claim and decided it on the merits for purposes of 28 U.S.C. § 2254(d).3 On its way to denying this claim, the Pennsylvania Superior Court found, as a matter of fact, that Boyd’s counsel “fully informed [Boyd] about the availability of the original plea offer, but [Boyd] decided to take his chances on the discretion of the court as to sentencing.” Boyd contests this factual finding.
Boyd first presented the second ground for trial counsel’s alleged ineffectiveness in his PCRA petition (i.e., on state collateral review), arguing that trial counsel provided ineffective assistance by rejecting the initial plea offer before discussing it with him. The PCRA Court did not recognize that Boyd’s claim was different from the one he had presented on direct appeal. It believed Boyd was again asserting that “guilty plea counsel was ineffective for advising defendant to reject a negotiated plea offer of four to eight years in light of the seriousness of the crimes charged,” rather than for rejecting the offer before consulting Boyd. Given this mistaken formulation, it is not surprising that the PCRA Court concluded “defendant raised the exact issue on direct appeal that he is now raising in his PCRA petition” and, accordingly, dismissed the claim as “previously litigated.” The Commonwealth concedes “the PCRA court misidentified Boyd’s ineffectiveness claim.” Commonwealth’s Suppl. Br. 5; see also id. at 6 n. 3 (“[T]he PCRA court incorrectly described the ineffectiveness claim ... and never correctly identifies it....”).
On PCRA appeal, however, the Pennsylvania Superior Court correctly identified Boyd’s claim, accurately describing the question presented as whether “trial counsel’s rejection of the [initial] offer before discussing it with [Boyd] rendered his assistance ineffective.” The Pennsylvania Superior Court correctly contrasted' this claim with Boyd’s claim on direct appeal that “his trial counsel was ineffective in failing to discuss a plea agreement in which [he] would have received a sentence in the mitigated range of the sentencing guidelines.” The highest state court to review Boyd’s petition, therefore, did not “misunderst[and] the nature” of his PCRA claim. Chadwick, 312 F.3d at 606. The Pennsylvania Superior Court rejected the PCRA claim on the basis of the “previously litigated” rule,4 but that disposition cannot mean the Pennsylvania Superior Court thought the claim was previously litigated, since as noted, that court, unlike the PCRA Court, correctly distinguished between the PCRA and direct-appeal claims.
Instead, the Superior Court looked back to its direct-appeal opinion and saw that it had already rejected the factual predicate of Boyd’s PCRA claim. Boyd’s claim that trial counsel was ineffective for rejecting *336an earlier plea offer before discussing it with him contains both factual and legal elements, and Boyd must establish both in order to prevail. First, he must show that, as a matter of fact, his trial counsel had rejected the initial plea offer before Boyd had an opportunity to consider it. Second, he must demonstrate that this factual state of affairs amounted legally to ineffective assistance of counsel, that is, that such behavior by Boyd’s counsel was constitutionally deficient and prejudiced him.5 The Pennsylvania Superior Court found Boyd could not establish the factual element of his claim because the court had already found on direct appeal that trial counsel “fully informed [Boyd] about the availability of the original plea offer, but [Boyd] decided to take his chances on the discretion of the court as to sentencing.” Accordingly, the Pennsylvania Superior Court adjudicated Boyd’s PCRA claim on the merits, rejecting it because the court had rejected its factual predicate at an earlier stage of the litigation. The Pennsylvania Superior Court therefore had no occasion to reach the legal question whether, if trial counsel had rejected the offer before consulting Boyd, such conduct would constitute ineffective assistance.
Whether the Pennsylvania Superior Court’s factual determination is “unreasonable” under 28 U.S.C. § 2254(d)(2)’s deferential standard is distinct from the threshold question of whether that standard is applicable in the first place. See Teti, 507 F.3d at 57 (“[T]he adequacy of the [state-court] procedures and of the decision are addressed through the lens of § 2254(d), not as a threshold matter.”).6 The state courts’ rejection of Boyd’s ineffective assistance of counsel claim is entitled to AED-PA deference because it is an adjudication on the merits. The Pennsylvania Superior Court recognized the distinct nature of Boyd’s PCRA claim. The Pennsylvania Superior Court disposed of Boyd’s claim on factual rather than legal grounds, but this means only that it is § 2254(d)(2) that applies to federal review of the claim.7 The Pennsylvania Superior Court relied on a finding made at a previous stage in the litigation, but this does not prevent its decision from being an adjudication on the merits. It means only that federal courts reviewing Boyd’s habeas petition should examine the Superior Court’s opinion on direct appeal, as well as its opinion on *337collateral review, in order to determine whether the state-court adjudication of Boyd’s claim was “unreasonable.”8
Since the state courts decided both variations of Boyd’s ineffective assistance of counsel claim on the merits, Boyd is eligible for relief only if he can satisfy the standards imposed by 28 U.S.C. § 2254(d). Accordingly, the District Court erred in exercising de novo review of Boyd’s claim. I would reverse and remand with instructions for the District Court to apply the proper AEDPA standards. See Terry Williams, 529 U.S. at 402-413, 120 S.Ct. 1495 (describing the difference between § 2254(d)’s standards and de novo review).
In the course of this appeal, other issues have arisen that should be dealt with on remand. One issue involves the federal evidentiary hearing held by the Magistrate Judge. Although both the Magistrate Judge and District Court relied on testimony from that hearing, neither the Magistrate Judge’s Report and Recommendation nor the District Court’s opinion appeared to examine whether the hearing complied with AEDPA, 28 U.S.C. § 2254(e)(2). That section provides:
If the applicant [for a writ of habeas corpus] has failed to develop the factual basis of a claim in State court proceedings, the [federal] court shall not hold an evidentiary hearing on the claim unless the applicant shows that—
(A) the claim relies on—
(i) a new rule of constitutional law, made retroactive to cases on collateral review by the Supreme Court, that was previously unavailable; or
(ii) a factual predicate that could not have been previously discovered through the exercise of due diligence; and
(B) the facts underlying the claim would be sufficient to establish by clear and convincing evidence that but for constitutional error, no reasonable factfinder would have found the applicant guilty of the underlying offense.
As Boyd does not contend that he can fulfill the conditions of either § 2254(e)(2)(A) or (B), the section’s opening clause is dispositive. If Boyd “failed to develop the factual basis” of his claim in state court, then he should not receive a federal evidentiary hearing.
In construing this opening clause, the Supreme Court has stated that “[t]he purpose of the fault component of ‘failed’ is to ensure the prisoner undertakes his own diligent search for evidence.” Michael Williams v. Taylor, 529 U.S. 420, 435, 120 S.Ct. 1479, 146 L.Ed.2d 435 (2000). Boyd *338argues that he was sufficiently diligent in seeking an evidentiary hearing in state court, and that § 2254(e)(2) is therefore no obstacle to the Magistrate Judge’s hearing. See id. at 437, 120 S.Ct. 1479 (“If there has been no lack of diligence at the relevant stages in the state proceedings, the prisoner has not ‘failed to develop’ the facts under § 2254(e)(2)’s opening clause, and he will be excused from showing compliance with the balance of the subsection’s requirements.”). The Michael Williams Court did not exhaustively explain what a petitioner must do to be deemed “diligent” under the statute, but it did state that “[djiligence will require in the usual case that the prisoner, at a minimum, seek an evidentiary hearing in state court in the manner prescribed by state law.” Id.
On remand, I would instruct the District Court to decide in the first instance whether Boyd’s efforts to obtain a state-court evidentiary hearing were sufficient to allow a federal hearing. If the court finds Boyd satisfied the diligence requirements of § 2254(e)(2)’s opening clause, it may again rely on the evidence adduced in the Magistrate Judge’s earlier hearing; otherwise, this evidence should be excluded.
The Magistrate Judge’s hearing, if permissible, raises another issue. We have held that “[a] district court may not reject a finding of fact by a magistrate judge without an evidentiary hearing, where the finding is based on the credibility of a witness testifying before the magistrate judge and the finding is dispositive of an application for post-conviction relief involving the constitutional rights of a criminal defendant.” Hill v. Beyer, 62 F.3d 474, 482 (3d Cir.1995) (citing United States v. Raddatz, 447 U.S. 667, 681 n. 7, 100 S.Ct. 2406, 65 L.Ed.2d 424 (1980)). This rule is grounded, at least in part, on prudential reasons. “Our judicial system affords deference to the finder of fact who hears the live testimony of witnesses because of the opportunity to judge the credibility of those witnesses.” Id. Although Boyd had testified at the evidentiary hearing held by the Magistrate Judge that he would have accepted the initial offer had he been adequately advised by trial counsel, the Magistrate Judge concluded that was not, in fact, the case. This finding necessarily implied a determination that Boyd’s testimony was not credible. Applying a de novo standard of review, the District Court, without holding a hearing of its own, rejected the Magistrate Judge’s determination and found that Boyd had satisfied the prejudice prong of Strickland. Boyd, 2007 WL 403884, at *5. I would hold that, if the District Court again reaches the prejudice prong of the Strickland test after applying the deferential standards of 28 U.S.C. § 2254(d), it should hold its own evidentiary hearing if it declines to adopt the Magistrate Judge’s finding.9
*339The Court of Appeals for the Second Circuit reached the same conclusion on a similar set of facts. Cullen v. United States, 194 F.3d 401 (2d Cir.1999). Petitioner Cullen had been tried and convicted of drug offenses and sought habeas relief on the ground that his trial counsel had failed to advise him adequately with respect to a plea bargain offer that, if accepted, would have resulted in a shorter sentence. The magistrate judge found that counsel had performed deficiently and that this performance had prejudiced Cullen, noting that “Cullen testified that if [defense counsel] had discussed the sentencing guidelines he would have pleaded guilty.” Id. at 403. The district court agreed as to the deficient-performance prong, but rejected, “without taking testimony,” the magistrate judge’s prejudice finding (based in part on the fact that Cullen had adamantly protested his innocence). Id. Accordingly, the district court denied the writ.
The Second Circuit vacated and remanded. Although the district court had characterized the issue as a matter of law, the Second Circuit noted that the prejudice question hinged on an “essentially factual determination.” Id. at 405; see id. (“[T]he determination of the likelihood that Cullen would have accepted the plea bargain if he had been fully informed of its terms and accurately advised of the likely sentencing ranges under the plea bargain and upon conviction after trial was, like all predictions of what might have been, a factual issue, albeit a hypothetical one.”). The district court had not simply asserted that it disbelieved Cullen’s self-serving testimony; it had pointed to other evidence, like his claims of innocence, that weighed against that testimony. Nonetheless, the Second Circuit recognized that the prejudice determination necessarily involved a credibility determination, id. at 407, and that pieces of evidence extrinsic to Cullen’s self-serving statement, like his claims of innocence and “the disparity between the guideline range [Cullen] faced and the range as represented by defense counsel,” were “faetor[s] bearing upon [Cullen’s] credibility.” Id. at 408. Accordingly, under the line of precedent including the Supreme Court’s decision in United States v. Raddatz and our decision in Hill v. Beyer, see Cullen, 194 F.3d at 405-07, the Second Circuit vacated the district court’s judgment and remanded, so that, “if the District Court [again] declines to accept any credibility findings made based on live testimony before the Magistrate Judge,” there would “be an opportunity for Cullen’s credibility to be assessed after the District Court has seen and heard him testify.” Id. at 407.
Cullen is instructive in another respect as well. The Second Circuit’s remand order assigned the case to a different district court judge. I would do the same here. This reassignment is dictated solely by concerns about the appearance of impartiality — concerns inherent in the procedural posture of the case, as Cullen recognized.10
For these reasons, I would reverse and remand to a different district court *340judge.11
. The District Court found that de novo review was also proper because "the state courts never cited or described the relevant federal precedent, and thus, never reached the merits of Petitioner's Sixth Amendment claim.” Boyd, 2007 WL 403884, at *2. The District Court erred in implying that the failure of a state court to state "the relevant federal precedent” is necessarily a failure to adjudicate a petitioner's claim on the merits. The Pennsylvania Supreme Court has made clear that the standard for ineffective assistance of counsel under Pennsylvania law— which the state courts applied here — is the same as Strickland’s standard, see Commonwealth v. Tedford, 598 Pa. 639, 960 A.2d 1, 12 (2008) (citing Commonwealth v. Pierce, 515 Pa. 153, 527 A.2d 973, 975 (1987) (adopting U.S. Supreme Court’s holding in Strickland)), so a Pennsylvania court has adjudicated a Strickland claim on the merits where it has applied the state-law standard to that claim. Rompilla v. Horn, 355 F.3d 233, 248 (3d Cir.2004), rev’d on other grounds sub nom. Rompilla v. Beard, 545 U.S. 374, 125 S.Ct. 2456, 162 L.Ed.2d 360 (2005).
. The Pennsylvania Superior Court expressly noted the question Boyd presented: "Where the prosecutor offered a negotiated guilty plea in the mitigated range of the guidelines, and the case against [Appellant] was so strong as to be untriable and also presented several reasons to expect a sentence in the aggravated range or above, was trial counsel ineffective in failing to discuss the relative merits of accepting the prosecution’s offer with [Appellant]?”
. Under Pennsylvania law, a petition for post-conviction review should be dismissed insofar as the "allegation of error” has been "previously litigated.” 42 Pa. Cons.Stat. Ann. § 9543(a)(3). "[A]n issue has been previously litigated if ... the highest appellate court in which the petitioner could have had review as a matter of right has ruled on the merits of the issue____” Id. § 9544(a)(2). Part III of Judge Hardiman’s opinion concludes that the "previously litigated” rule is not a procedural default rule. I agree.
. The prejudice prong of Strickland calls for another factual determination: Would the defendant have avoided the injury of which he complains if counsel had not performed deficiently? The petitioner can prevail only if the court answers this question in the affirmative.
. Judge Sloviter's opinion states that the Superior Court's direct-appeal opinion "was clearly based on 'an unreasonable determination of the facts in light of the evidence presented in the state court proceeding,’ and [is] therefore not entitled to the deference required by AEDPA.” Judge Sloviter Op. at 346 (quoting 28 U.S.C. § 2254(d)(2)). But this formulation, I believe, does not distinguish between the threshold question of whether AEDPA deference is due — that is, whether § 2254(d)’s standards apply — and the question of whether Boyd is entitled to relief under AEDPA’s standards.
. Since the Pennsylvania Superior Court rejected the factual predicate of Boyd's PCRA ineffectiveness claim, it did not have occasion to apply either prong of the Strickland test. Accordingly, if Boyd is able to show that the state-court factual determination was "unreasonable” under § 2254(d)(2), and that his trial counsel did reject the initial plea offer before consulting him, the District Court should apply the two prongs of the Strickland test de novo. See Rompilla, 545 U.S. at 390, 125 S.Ct. 2456 (examining the prejudice prong of a Strickland claim de novo because the state courts, having unreasonably found counsel’s performance adequate, never reached that issue).
. This case is distinguishable from those in which the highest state court of relevance failed to recognize the nature of the petitioner's claim and thus failed to adjudicate petitioner's claim “on the merits” for purposes of § 2254(d). When a state court erroneously believes a claim has been previously litigated, and dismisses the claim on that ground, there is no state-court decision on the merits. See, e.g., Cone, 129 S.Ct. at 1784 (holding that a claim had not been adjudicated on the merits where state courts had found it to have been previously litigated (and dismissed it on that ground), but in fact it had not been). The PCRA Court here made this mistake. If its decision had been the final state-court word on the matter, Boyd's PCRA claim would not have been adjudicated on the merits, as was the case in Cone. But on PCRA appeal, the Pennsylvania Superior Court correctly recognized Boyd's claim and correctly found that the factual issue underlying that claim had been previously decided. When state courts correctly find that an issue has been previously litigated, the question on federal habeas review is not whether § 2254(d)’s standards apply (they do), but rather to which state-court opinion we should apply them. Cf. Bond, 539 F.3d at 289-90 (Where a lower state-court opinion "represents the state courts’ last reasoned opinion on [the relevant issue],” we should "look through” the higher state-court opinion and apply § 2254(d)’s standards "to the highest reasoned opinion.”).
. Such a hearing might have the additional benefit of further developing the factual record in light of the issues that have surfaced in the course of this appeal. It might also illuminate the parties' continuing factual dispute over the specific sentencing term proposed in the initial plea offer. Boyd has contended that the offer was for a term of incarceration of four to eight years, whereas the Commonwealth has maintained the offer was for a term of four to ten years. Although the District Court order conditionally granting the writ describes the term as four to ten years, its accompanying Memorandum and Order refers to both terms at different points without clarification. This factual dispute could be relevant to the determination of an appropriate remedy if the District Court reaches that issue again on remand. The details of the plea offer could also bear on the prejudice prong of the Strickland test insofar as the length of the proposed sentence affects the likelihood that Boyd, if properly advised, would have accepted the initial plea offer instead of taking his chances with an open plea.
. If the original district court judge were to reach the same conclusion after hearing Boyd’s live testimony, those
unaware of [the district court judge's] deserved reputation for fairness, would wonder whether the Judge had permitted h[er] prior ruling to influence h[er] second decision. There are occasions when a matter is appropriately remanded to a different district judge not only in recognition of the difficulty that a judge might have putting aside h[er] previously expressed views, but also to preserve the appearance of justice .... [T]hat course is warranted here.
Cullen, 194 F.3d at 408 (internal quotation marks omitted).
. I express no opinion about the ultimate merits of Boyd’s claim.