BOSTON (CBS) — Daniel Theis left Monday night’s Celtics win in Atlanta with a sprained ankle, an injury that will now cost him Wednesday night’s game against the Orlando Magic.

The Celtics have already ruled Theis out for Wednesday night’s visit from the Magic, part of a rather lengthy injury report the team sent out Tuesday afternoon. The good news is Theis and center Robert Williams — who has been out since Dec. 6 — are the only players ruled out for Wednesday’s game.

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Guards Kemba Walker and Marcus Smart — both of whom missed Monday night’s game — are both questionable for Wednesday’s tilt.

Theis went down with the injury in the third quarter, and it did not look pretty. He was on the floor for a few minutes before he gingerly made his way to the Boston locker room with the help of team trainers. Theis eventually returned to the bench and was deemed available to play, but did not see the floor again. He told reporters after the game that his ankle swelled up while he sat, ending any chance of a return to action.

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“When I walked out I was ready to go back in, but the other guys were playing well,” Theis said, via MassLive’s Tom Westerholm. “Then at one point, I was sitting and it got cold and a little stiff and I said, ‘All right, I can’t go back in. Because if I get cold and can’t move the right way, I can’t help the team.’ And they played well.”

Theis was optimistic that he’d be able to play Wednesday night, but that is no longer the case, leaving Boston’s frontcourt pretty shorthanded against the Magic. Boston’s starting center, Theis has averaged 8.1 points and 6.1 rebounds for the Celtics this season. Theis is an important part of Boston’s rotation, especially on a team that doesn’t have much size on the roster.

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The Celtics are reportedly chatting with the Houston Rockets about a Clint Capela trade and remain interested in Washington sharpshooting big Davis Bertans. Either move may become a lot more necessary if Theis is sidelined for a chunk of time. The NBA trade deadline is 3 p.m. on Thursday.