Boston Celtics coach Doc Rivers ruled Shaquille O'Neal out for Sunday's Game 4 of the Eastern Conference quarterfinals against the New York Knicks, noting the 39-year-old center simply is not ready for game action.

O'Neal was present at Madison Square Garden on Saturday as the Celtics engaged in a walk-through after watching film at the team hotel.

"He's not playing [Sunday]," said Rivers. "We didn't do anything to see honestly. We didn't practice, we just walked through. I'm not going to put him out on the floor."