Jared Sullinger did not practice with the Celtics on Thursday because of back spasms, and coach Doc Rivers said he is 50-50 to play Friday against the Orlando Magic.

Sullinger apparently slipped in the draft because of back issues but has played in the team’s first 45 games. He left Wednesday’s win with 7:52 left in the first quarter and did not return.

Rivers said Sullinger began experiencing back discomfort two weeks ago, but the coach doesn’t expect it will be a major injury.

“There’s nothing, I don’t think, that is bad, just spasms,” Rivers said. “When you have a back, you have a back, it’s not one thing, it’s everything.

“I’m not that concerned. Can his miss games here or there? He may, but it’s not anything [long-term] or anything like that.

“My guess is he plays with it every day. I keep saying, because I had a back injury my whole career, once you have a back, you have a back. It never goes away. You just have to play through it.”