From The New York Times:

Mariano Rivera and Jason Giambi played in yesterdays doubleheader, so their health status is not alarming to the Yankees. But the team was concerned enough about them to schedule magnetic resonance imaging exams.

Rivera has experienced inflammation in his right elbow and will have a precautionary M.R.I. on the elbow soon, perhaps today. He earned the save in the first game yesterday but did not pitch in the second. ...

Giambi had an M.R.I. on his left wrist between games of the doubleheader, after he went 1 for 3 with a sacrifice fly as the designated hitter in the opener. He missed a start Sunday in Anaheim because of cramping in his hands, and he has had his wrist wrapped lately.