Celtics' Paul Pierce had fluid trained from his infected right knee on Wednesday. (Michael Dwyer/Associated Press)

The Boston Celtics don't expect Paul Pierce back any time soon.

Pierce was in so much pain from a knee infection that coach Doc Rivers says the all-star NBA forward called team trainer Ed Lacerte on Wednesday around 3 a.m. ET.

Lacerte went to Pierce's house and took him to hospital and his right knee was drained.

Pierce, who didn't make the flight to Orlando for the Christmas Day game against the Magic, is expected to miss at least two weeks.

"What he's going through is pretty significant," Celtics guard Ray Allen said. "It is serious. Because me knowing Paul, he's always practising and he's always playing, so for him not to be here, it must be very significant."

Pierce, the 2008 NBA finals MVP, had played in every game this season, leading the team with an average of 18.2 points per game. Pierce complained of soreness in his knee after Tuesday night's game, when he missed his first 10 shots against the Indiana Pacers but wound up scoring 21 points in the win.

The team left the arena thinking he was fine.

"It's amazing, he won the game for us the night before and he woke up in the middle of the night hurting," Rivers said.

The Celtics are on a six-day, four-game road trip that will also take them to the Clippers, Golden State Warriors and Phoenix Suns before returning home for a Jan. 2 game against Toronto. Rivers said it was doubtful Pierce would join them on the trip.

Star forward Kevin Garnett is expected to play against Orlando after missing the last game with a thigh bruise.

Glen (Big Baby) Davis also practised, but Rivers said he's unlikely to play Friday because the forward is still recovering from a broken right hand.