Posada -- serving as the designated hitter -- singled in the sixth inning and moved to second base on a Melky Cabrera groundout. The inning ended a batter later, and Posada was replaced by Hideki Matsui when his spot came up again in the eighth inning.
"He said he felt it grab," Yankees manager Joe Girardi said. "It's not something that we need at this point. It's something we'll have more of an answer on after his MRI."
Girardi said that he could not estimate the severity of Posada's injury but that he would discuss with general manager Brian Cashman whether the Yankees needed to call up another catcher. Jose Molina is the only other backstop on New York's roster.
"I'm not sure how bad it's going to be, but he won't be playing [Tuesday], I can tell you that," Girardi said.
Yankees shortstop Derek Jeter expressed hope that Posada -- who entered Tuesday hitting .312 with five home runs and 20 RBIs in 23 games this season -- will not be lost for a long period.
"I haven't even found out exactly what is wrong with him, but you don't like hearing he might be out for an extended period of time," Jeter said. "Hopefully, you wish for the best -- especially with him coming back from missing most of last season. You hope that he's all right."
The only other catcher on the Yankees' 40-man roster is Francisco Cervelli, who is currently playing at Double-A Trenton.
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.Less