By Gary Washburn, Globe Staff

WALTHAM -- The Celtics returned to practice Friday afternoon in preparation for their Game 1 Eastern Conference semifinals matchup with the Philadelphia 76ers. Coach Doc Rivers said the team would not go through a full practice but rather spend more time watching film of the 76ers, who won two of three meetings against the Celtics this season.

Rivers said he is "concerned" with the sprained left MCL of Paul Pierce and the sore right ankle of Ray Allen. He would not put a percentage on their chances of playing tomorrow but Pierce told reporters he plans to play.

Allen, on the other hand, said the ankle has regressed the past few days and would spend Friday in treatment.

"It's no better, I'll get treatment and stay off of it the rest of the day," he said. "Ill see how I feel (tomorrow). It puts you somewhat in a disappointing mood, frustrating, you come and do what you can. Whatever I feel, I just build on that."

A more subdued Kevin Garnett than following the Game 6 win over the Atlanta Hawks spoke with the media about the 76ers.

"A tough team man," he said of Philadelphia. "They probably have five to seven guys who average double figures that can kill you night in and night out and they play very, very hard. They play with a lot of energy. They play together. (Coach) Doug (Collins) has those guys believing. They're not talking a lot. They're coming out, showing up to play. They're playing with a lot of confidence."

Also, Rivers said on the game's final sequence Marquis Daniels was supposed to be defending the inbounds pass and not Al Horford. There was a mix-up between Daniels and Garnett on defense. Daniels, giving away four inches and 50 pounds, fouled Horford when he received the pass and Horford missed the first of two free throws that could have tied Game 6 with 2.3 left.