Well here's the thing. They held onto a lead against the Cavs for three quarters, and then they ended up losing by 20. I don't think Paul Pierce prevents us from losing by 20. Paul Pierce would not have single-handedly prevented the total collapse on both ends of the floor that this team had in the fourth quarter - not even a healthy Paul Pierce.
Paul Pierce is not a top 10 player in the league. He is not Kobe, Melo, Wade, or LeBron. His absence is not enough of an excuse to explain a blowout loss after being up by 13. Paul Pierce can't account for a 33 point turnaround between the second quarter and the end of the fourth.
Sorry, but this team lost soundly and even if Paul Pierce had been healthy and playing that alone would not have been enough of a difference. The Celtics - every single player on the team - lost the game last night, a game they could have won. It wasn't like they came close but couldn't quite manage it. They fell apart and were demolished.