According to the Celtics Twitter page, Paul Pierce suffered another stinger in practice today and is questionable for Wednesday night's game against Oklahoma City.
WEEI.com has more information on how the injury happened:
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
“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.”
WEEI is also reporting that Kendrick Perkins should be back on the court for Wednesday's game.