WALTHAM — Avery Bradley ‘s shoulder popped out of place early in the second half of Game 4, but at some point between the time he walked off the court in agony and the time he reached the end of the bench, trainer Eddie Lacerte was able to pop it back into place.
“It’s just tough. It really is. I swear a lot of people would not be playing, and the only reason he is is because he wants to,” Doc Rivers  said on Sunday before the team conducted practice. “I am concerned at some point that he may not be able to anymore. We don’t know what game that is, we don’t know what day he can finish it. We can keep going all the way and he can play [or] tomorrow could be his last game.”
The 21-year-old Bradley has impressed his teammates with his toughness, but they also know that there’s a line and he’s right on the verge of crossing it.
“A lot of young players would probably sit down, worry about their future, their career,” Paul Pierce  said. “At the end of the day, Avery has to do what’s best for him and his family and possibly for the long run. Hopefully he doesn’t have any long-term injuries due to the fact that he’s playing. I think it’s a fine line there, too.”
There’s the issue for the Celtics . They are 18 points better with Bradley on the court than when he’s off — the second-best mark behind Kevin Garnett ‘s absurd plus-56. When Bradley picked up his fourth foul early in the second half of Game 4, they were ahead by 18 points. When he returned, they were down by one.
“We don’t ever do it the easy way, but I don’t know if we could,” Rivers said. “Not because of the mental, just because we are thin. There are times we do break and it’s more for other reasons than basketball.”
It’s not just Bradley, of course. Ray Allen  is playing through bone spurs that would likely put him on the sidelines if it was the regular season. Mickael Pietrus  and Pierce have knee issues. Every team in the league has injury issues, but few teams left in the postseason are as thin, or as old, as the Celtics.
“That’s the scariest part of our team,” Rivers said. “I’ve said it for three months. We are very thin. We don’t have a big margin for error. We don’t have it even when guys are healthy. Our good players have to play well to give our bench guys a chance to stay on the floor longer, which allows us to get more rest. There’s a minute number in every game that I’m concerned with our starters. When they get over that, we struggle. There’s a lot of things going on in a game every night for us. Quite honestly a lot of teams don’t have to deal with, but we do and we know that.”