WALTHAM — For the second time in three days, Paul Pierce  injured his right shoulder. This time, the injury happened midway through Celtics  practice when he ran into a back screen and fell to the ground. Rivers said trainer Ed Lacerte said if it’s just a stinger, Pierce should be fine to play.
“He actually got hurt again,” Rivers said. “It’s a stinger. It was the same exact reaction. It looked worse today. Eddie said if it’s a stinger, he’ll be fine but you get concerned because it’s a game and a practice, exact same thing.”
‘That’s something you play a guy five minutes and that can happen, Rivers added. ‘There’s nothing you can do about that. The good news is it’s not a shoulder separation or anything and probably the worst case is he misses a game or two, at worse. That’s not all bad and obviously, you’d like to have him and it’s not a lower body injury.’
Meanwhile, Kendrick Perkins , who has missed the last two games with left knee tendinitis, is expected to return to the starting lineup on Wednesday night against Kevin Durant  and Oklahoma City at TD Garden.