I'd be VERY surprised if Perkins plays, given the nature of the injury. Bynum's issues may well negate that loss.
The bottom line is effort. Rebounding is effort and attention to detail. We have to have it, or we're going to lose Thursday night. That will have MUCH more of an impact on the game than Perkins.
CoachBo is right--Game 7, like every other game in the Finals, will be all about EFFORT. For one game, we can overcome the loss of Perk and LA's homecourt advantage--if we come out with supreme effort, defend the perimeter, box out, and make all the 50/50 plays.
This team plays loves being the underdog and right now everyone, outside of hardcore Celtic fans, is assuming that Game 7 goes to the Lakers. This creates pressure on the Lakers and motivation for the Celtics.
The blowout loss in Game 6 also creates momentum for Game 7, much like Game 1's loss created Game 2's win. The Lakers are human, and the beatdown in Game 6 will cause some of them to let down in Game 7.
Perk's injury, while debilitating for our defense and toughness, makes this team much harder to defend. And even though we were completely outplayed in Game 6, the Lakers still didn't break 90. The Celtics will come to play defensively on Thursday, but they'll only win if they're able to make shots. Having Sheed and Baby in there will create more lanes for Rondo, and hopefully will minimize the scoring lulls that seem to hit us every game. We'll still need to make shots, but Baby and Sheed are vastly superior to Perk when it comes to catching the ball, converting in traffic, hitting jump shots, and making the defense respect them. This is all good news for our offense.