Just saw it again, I can provide a bit more info. 8th inning, Pujols singles. On the way to first, his stride clearly shifts to a limp. He visibly favors his leg, wincing and hobbling.
BT then mentioned something about how an official with STL later said "his knee was barking." Then the baseball tonight guy said, "that doesn't sound fun," or something to the effect.
The point to the story: Pujols was running. His run broke into an obvious limp, and the story is that something was wrong with his knee.