Alex Rodriguez is a lock to win the AL MVP. But because of the position he plays, catcher Jorge Posada may be the most indispensable Yankee. That's why it was scary to see Posada get knocked over by Eric Hinske in a violent sixth-inning collision at the plate yesterday in a 10-1 Yankees loss at Fenway Park. While awaiting Robinson Cano's throw, Posada braced for the collision with Hinske, who was running from third, by putting his entire body in front of the plate. That gave Hinske no other option but to try and dislodge the ball from Posada's glove. An elbow-first dive into Posada didn't jar the ball loose and Hinkse was called out. Posada was shook up and took a few minutes to clear his head. He stayed in the game but left after the seventh and was taken to Mass General Hospital for tests. A CT scan of Posada's neck and head were negative. He is listed as day to day. "He got his bell rang pretty good," Joe Torre said. "Hopefully he is good (today). He had a headache. As they continued to score the headache got worse. We sent him to the hospital. Dr. (Stuart) Hershon wasn't that concerned."