Gary Washburn of the Boston Globe reports (via blog):

Shaq returns for Celtics, then quickly strains right calf

Just minutes after Shaquille O’Neal wowed the crowd with 6 points in his first game in two months, he was limping back to the locker room with 11:11 left in the second quarter of the Celtics’ game against the Detroit Pistons. The team said it is officially a strained right calf and he is uncertain to return.

Playing for the first time since Feb. 1, O’Neal was in for his second stint of the game when he suddenly began limping, heavily favoring the right leg.