dissenting:
I respectfully dissent.
The majority opinion correctly notes that state law governs the substantive rights of the parties in this diversity litigation. Specifically, the opinion properly relates the basic state-law principle that a subrogee stands in the same position as an assignee — “in the shoes of the subrogor or assignor.” Slip op. at 4. The opinion essentially adopts Cessna’s conclusion that since an insurer as subrogee has no greater rights than the subrogor and because Goodfellow failed to assert as a counterclaim the claim for indemnity or contribution against Cessna (now asserted by Avem-co) in response to Cessna’s third party complaint, Avemco is now barred by Federal Rule of Civil Procedure 13(a) from asserting that same claim for indemnity or contribution against Cessna. Brief of Appellee at 13-15.
*1002I disagree with the latter conclusion. The majority’s syllogism ignores the consequences of the earlier full subrogation to Avemeo of Goodfellow’s indemnity claim upon Avemco’s payment to Kasamis. The substantive rights here are premised on state law. But the dispositive procedural rules here are derived solely from federal law, specifically the impact of Rules 13(a) and 17(a) of the Federal Rules of Civil Procedure. See American Fidelity & Casualty Co. v. All American Bus Lines, 179 F.2d 7, 10 (10th Cir.1950).
The majority opinion accurately outlines the facts underlying this appeal. It is helpful, however, to focus on these basic points which bring the issue before us into proper perspective. First, the informal personal injury claim of the passenger Kasamis against the pilot Goodfellow was settled by Avemeo, Goodfellow’s insurer, with a release obtained on May 27,1986, for Goodfellow, Avemeo and others. Appellant’s App., Exh. C at 14-18 (hereafter App.). Avemeo’s settlement checks to Kasamis for $102,500 were dated June 10, 1986. Id. at 12. The federal court complaint of the other passenger Barker against Cessna and others was filed June 6, 1986. (Barker’s separate suit against Good-fellow and another party was filed November 21, 1986.) Id. at Exhs. D and A. Cessna’s third party complaint against Goodfellow and Goodfellow Corp. for indemnity was filed in that first Barker case on August 24, 1986. Id. at Exh. E. Then Goodfellow’s answer to Cessna’s third party complaint was filed September 23, 1987. Id. at Exh. F.
This chronology makes it clear that before any claim was asserted by Cessna against Goodfellow and before Goodfellow was called on to file a responsive pleading thereto, full subrogation of any rights of Goodfellow against Cessna for indemnity or otherwise had occurred by operation of law. Thereafter those rights were possessed only by Avemeo, which was not a party in the Barker suit against Cessna. Rule 13(a) only required assertion against Cessna of any claim that Goodfellow had when he answered Cessna’s third party complaint. “A pleading shall state as a counterclaim any claim which at the time of serving the pleading the pleader has ... .against any opposing party-” Fed.R.Civ.P. 13(a) (emphasis added).
Our first question turns on identification of the real party in interest: who could assert the indemnity claim against Cessna when Goodfellow answered Cessna’s third party complaint against him? The answer may be found partly in the law of subrogation which determines the relevant substantive rights vis-a-vis Cessna,1 and partly in federal procedural law applying Rule 17(a), which determines how those rights may be asserted in federal court. Brocklesby Transport v. Eastern States Escort, 904 F.2d 131, 133 (2d Cir.1990) (“in diversity cases federal law governs the issue of in whose name a lawsuit must be brought, even though state law controls the underlying substantive right of an insured to recovery”); Garcia v. Hall, 624 F.2d 150, 152 n. 4 (10th Cir.1980) (same).
Once subrogation had been triggered by Avemco’s settlement payment to Kasamis, Rule 17(a) permitted only Avemeo to assert any claim for indemnity against Cessna. “If the subrogee has paid an entire loss suffered by the insured, it is the only real party in interest and must sue in its own name.” United States v. Aetna Casualty & Surety Co., 338 U.S. 366, 380-81, 70 S.Ct. 207, 215, 94 L.Ed. 171 (1949); Kansas Electric Power Co. v. Janis, 194 F.2d 942, 944 (10th Cir.1952) (“And where ... the insurers pay the owners in full for the loss and become subro-gated to all of the rights of such owners against the alleged wrongdoer, the action against the alleged wrongdoer to recover in tort must be maintained in the name of the insurers”).2 Accordingly, at the time that *1003Goodfellow’s answer to Cessna s third party complaint was filed, Goodfellow did not have the indemnity claim against Cessna. Avem-eo fully possessed it as subrogee.
Thus there was no failure by Goodfellow to state any claim for indemnity in violation of the requirement of Rule 13(a). After subro-gation occurred by operation of law, Goodfel-low was not entitled to assert the counterclaim in his own name. American Fidelity & Casualty Co., 179 F.2d at 10. (After sub-rogation, the insured “is not entitled to bring an action in his own name against the third party tortfeasor.”). And when Avemco asserted its claim for indemnity in the instant suit, there was no defense or impediment attached to that claim because no such defense ever arose against the subrogor Good-fellow, who had not failed to assert a claim he could make against Cessna. Although Avemco is standing in Goodfellow’s shoes, Avemco cannot be saddled with a claimed violation by Goodfellow of Rule 13(a) because such a violation never occurred.
Turning to the other federal rule involved here, Rule 13(a) makes compulsory any counterclaim “which at the time of serving the pleading the pleader has against any opposing party, if it arises out of the transaction or occurrence that is the subject matter of the opposing party’s claim_” (Emphasis added). The plain language of the rule precludes a holding that Avemco’s indemnity claim against Cessna could and should have been asserted as a compulsory counterclaim in the Barker litigation. Avemco was not the “pleader” of Goodfellow’s answer to Cessna’s third party complaint against Goodfellow in the Barker case. Goodfellow alone was. The term “pleader” refers only to “the party asserting a particular pleading.” Black’s Law Dictionary, p. 1152 (6th ed. 1990). The term “party,” in turn, means “a person whose name is designated on record as plaintiff or defendant.” Id. at 1122 (emphasis added). Avemco never filed a pleading in Barker, nor was it designated on record as a party. Instead, its sole function there was to provide Goodfellow with a defense to claims made against him, pursuant to its insurance contract.
Moreover, because Cessna’s third party claim was against Goodfellow and not Avem-co, Cessna cannot be characterized as Avem-co’s “opposing party” in Barker within the meaning of Rule 13(a). This court has held that “an ‘opposing party’ must be one who asserts a claim against the prospective counter-claimant in the first instance. The very concept of a counterclaim presupposes the existence or assertion of a claim against the party filing it.” First Nat. Bank in Dodge City v. Johnson County Nat. B. & T. Co., 331. F.2d 325, 328 (10th Cir.1964). As stated in Nancy’s Product, Inc. v. Fred Meyer, Inc., 61 Wash.App. 645, 811 P.2d 250, 253 (1991):
Words contained in court rules which are not therein defined should, like statutory terms, be given their ordinary meaning. ... To interpret the term “opposing party” in the context of the court rules so as to include a nonparty with an adverse interest is a non sequitur. We hold that an opposing party for purposes, of [Washington Superior Court Civil Rule] 13(a) is one who asserts a claim against the prospective counter claimant in the first instance. First Nat’l Bank v. Johnson Cy. Nat’l Bank & Trust Co., 331 F.2d 325 (10th Cir.1964).
To argue, as Cessna implicitly does, that because Avemco was a potential party in the Barker litigation it was required by Rule 13(a) to join (or be joined) in order for it to assert its indemnity claim against Cessna “really assumes the point it should be making. For it is only in the event that [the relevant] claim in fact met all the criteria of a compulsory counterclaim as outlined in Rule 13(a) that additional parties must have been brought in by the court had the coun-terelaimant so requested.” Mesker Brothers Iron Co. v. Donata Corp., 401 F.2d 275, 280 (8th Cir.1968) (emphasis in original).
*1004As noted, Avemco was not a party to the Barker suit. Avemco also was under no compulsion to seek to intervene in that earlier case. Cf. Martin v. Wilks, 490 U.S. 755, 763, 109 S.Ct. 2180, 2185, 104 L.Ed.2d 835 (1989) (“a party seeking a judgment binding on another cannot obligate that person to intervene....”); Mann v. City of Albany, 883 F.2d 999, 1005 n. 2 (11th Cir.1989) (“The Supreme Court’s opinion in Martin expressly eschews a regime of mandatory intervention.”).3 Only if Avemco had in fact joined or been joined as a party in the Barker suit would it conceivably have become subject to the mandate of Rule 13(a). Montgomery Ward Dev. Corp. v. Juster, 932 F.2d 1378, 1383 (11th Cir.1991) (“Weigel was a potential defendant who was not joined in the prior action, and thus does not qualify as a pleader for purposes of the compulsory counterclaim bar”); Ponderosa Dev. Corp. v. Bjordahl, 787 F.2d 533, 536 (10th Cir.1986) (“Although plaintiffs moved to join [the present] defendants and to pursue [the present] claim in the foreclosure suit, their motion was denied. An attempt to implead additional parties is materially different from a claim against an already existing party under Rule 13(a).... Because plaintiffs’ claim against defendants was not against an opposing party in the earlier action, it is not barred by the compulsory counterclaim doctrine.”); see also Birmingham Fire Ins. Co. v. Winegardner and Hammons, Inc., 714 F.2d 548, 551-52 (5th Cir.1983) (proposed claim against parties to be impleaded did not constitute compulsory counterclaim against an already opposing party).4
As it stands, Avemco was never made a party to the Barker litigation. Its indemnity claim against Cessna therefore neither could nor should have been the subject of a compulsory counterclaim therein and Avemco is not now barred from asserting its indemnity claim in this separate action.
. The doctrine of equitable subrogation appears to be generally recognized. See, e.g., American Fidelity & Casualty Co., 179 F.2d at 7, 9-10 and n. 1 (citing numerous state and federal cases as showing that ‘‘[o]rdinarily when a public liability insurance company fully reimburses its insured for losses within the coverage of the policy, it becomes subrogated to the rights of the insured against third parties whose tortious conduct caused the loss”).
. See also Gas Service Co. v. Hunt, 183 F.2d 417, 419 (10th Cir.1950) (same); American Fidelity & Casualty Co., 179 F.2d at 10 (same); Krueger v. Cartwright, 996 F.2d 928, 932 (7th Cir.1993) (same); Brocklesby Transport v. Eastern States *1003Escort Servs., 904 F.2d at 133 (same); 6A Charles A. Wright, Arthur R. Miller & Mary K. Kane, Federal Practice & Procedure 1546 (2d ed. 1990) (“The general rale in the federal courts is that if the insurer has paid the entire claim, it is the real party in interest and must sue in its own name.”).
. The majority opinion argues that policy supports its position; that Rule 13(a) is designed to promote joinder of related claims in the same litigation; and Rule 17(a) is designed to reduce the threat of multiple litigation. I do not disagree with these propositions, but they in no way overcome the fact that the Supreme Court expressly eschewed “a regime of mandatory intervention” in Martin.
. In this regard, Rule 13(a) follows the general principle that “a person cannot be deprived of his or her legal rights in a proceeding to which such person is neither a party nor summoned to appear in the legal proceeding.” Jansen v. City of Cincinnati, 904 F.2d 336, 340 (6th Cir.1990).