The Mets activated catcher Mike Piazza off the 15-day disabled list Saturday. He then had to leave New York's 4-2 loss to the Cardinals in the eighth inning after being hit in the head with a pitch from Julian Tavarez. Piazza, who started and finished 2-for-3 with a homer, had been out since suffering a broken left hand on August 17 when catching versus Pittsburgh. He is listed as day-to-day after this latest incident, suffering a slight concussion. Cardinals manager Tony La Russa spoke to Tavarez in the dugout immediately after the incident. "My whole concentration on the game is affected by a pitch that got away," La Russa said. "You know, that looks so terrible. The guy is a great pro. I just talked to Julian in there for a long time. Nothing against him, as soon as he fell out of his delivery...the ball has to get down. He's a sinker ball pitcher. That incident screws up the whole night for me." Piazza is batting .263 with 15 homers and 56 runs batted in this season. The 12-time All-Star is seven homers shy of 400 for his career.