concurring in part and dissenting in part.
I do not believe that Diaz’s suit is barred by principles of res judicata. In addition to determining whether the claim in the instant suit “could properly have been raised in the earlier suit,” ante at 562, I believe the court must also ascertain whether the claim presented here is such that one would normally expect a litigant to have joined it with the claims presented in the prior suit. Cf. 18 Wright, Miller & Cooper, Federal Practice and Procedure § 4407, at 49-54 (1981) (analyzing the concept of res judicata merger under the principles governing the mandatory joinder of claims). Diaz’s damage claim does not pass this test.
I agree with the majority that Diaz’s employment contract does not give him the right to commissions on sales booked after Diaz terminated his employment. But I would award Diaz commissions on sales booked before he terminated his employment even though the shipments did not occur until after he left Indian Head. The contract is, as the majority also concludes, ambiguous on this point. But bearing in mind the principle recognized by the majority “that because Indian Head drafted the employment agreement, any ambiguities therein must be construed against Indian Head,” ante at 564; see ante at 567, I interpret paragraph three of the contract to give Diaz commissions earned on all booked sales “[djuring the period he [was] employed at Indian Head.” Moreover, this interpretation of the contract is. supported by the payment of commissions in advance of shipment (but after booking) in January 1974. I would not rely on Indian Head’s explanation of the practice, namely that Indian Head adopted this approach gratuitously to placate Diaz. I would give weight to the practice as a contemporaneous construction of the contract. Hence, I would *570award Diaz damages for the amount of commissions earned, based upon sales booked at the time he left Indian Head’s employ.
To this extent, I respectfully dissent.