Is Marino Rivera's career with the Yankees over ? Injury is very critical.

New York Yankees pitcher Mariano Rivera, one of the greatest closers in baseball history, could be finished becuase of his torn ACL in a crazy injury Thursday night.

Mo twisted his right knee while shagging fly balls during batting practice before the Yankees' game in Kansas City. He immediately crumpled to the ground holding the knee ... and had to be removed from the field on a cart. According to the Yankees, an MRI revealed the torn ACL -- and he'll most likely be out for the rest of the season. 42-year-old Rivera has 608 saves -- the most of all-time -- and is a lock for the Hall of Fame. Even before the injury, Yankees fans were terrified he might retire after this season. After the game a reporter asked Mariano if he would return next season -- and while fighting tears he said, "At this point...I don't know. We have to face this first."

(TMZ)