Yankees catcher Jorge Posada left in the eighth inning of Monday night's loss to the Red Sox with a hamstring injury. Hideki Matsui pitch-hit for Posada, who was playing as New York's designated hitter, after he came up lame on the bases earlier in the game. Posada with 2-for-2 with a walk in the 6-4 loss, and is scheduled to have an MRI on Tuesday.