Doc: Pierce 'doubtful' but not ruled out

WALTHAM, Mass. -- Boston Celtics coach Doc Rivers said that captain Paul Pierce did not participate in any of Friday's practice session and remains "doubtful" for Sunday's season-opener against the Knicks on Christmas Day.

Rivers noted the team will attempt to put Pierce through a practice before departing for New York on Saturday and will consider playing him -- likely in a reserve role -- if he gains medical clearance. Sasha Pavlovic is expected to start if Pierce, who has missed much of training camp and both preseason games with a bruised right heel, is unable to go.

"No, he didn't do anything [Friday]," Rivers said. "He seems to be working more -- as far as working out. We'll see [Saturday]. I still think it's doubtful [he'll play], but we'll see.

"Tomorrow we'll know better. But he could be [available]. Paul may wake up and say, 'Coach, I want to go.' I can tell you this, it'd be very unlikely he'll start if he plays. I don't think that will happen. So if he does play, he'll play 15 to 20 minutes, but right now I don't see him going."

Rivers said it comes down to the medical staff and trainer Ed Lacerte giving him a green light to play.

"It's medical staff decision -- 100 percent a medical staff decision," Rivers said. "I think this year it's really going to have to be that. Because we can't trust [the player] in that. Because if they do play and risk further injury, then miss some games, that's [like] 25 games because it's a shortened season."

Pavlovic started Wednesday's exhibition finale and spent much of the week working with the first unit in order to preserve the continuity of the second unit, most notably keeping Marquis Daniels with the reserves in case Rivers operates with a full five-man bench unit on the floor during Sunday's game.

Chris Forsberg covers the Celtics and Patriots for ESPNBoston.com.