Scalabrine said he has had five concussions in his life - three of them this year. He had two in a week in January and sat out nine games; he returned and played three games before an injury against Denver on Monday that was first described as a strained neck but was likely another concussion.

"We're just going to be very careful with him," Celtics coach Doc Rivers said. "I'm pretty scared. I don't know anything about it, but I know enough to be scared. We really don't know enough about it in any league."