UPDATE (8:31 p.m. ET) Daniel Theis has returned in the third quarter.

UPDATE (8:22 p.m. ET): The Celtics announced at halftime that Theis is questionable to return with an ankle sprain.

ORIGINAL STORY: The Celtics already were thin in their frontcourt heading into Friday’s home opener against the Toronto Raptors with Enes Kanter out.

And things got worse for Boston in the second quarter.

Daniel Theis was backpedaling on defense when he appeared to injure his ankle. The center remained down in visible pain before hobbling off the court and into the locker room.

According to NBC Sports Boston’s Abby Chin, Theis needed assistance after getting himself off the court.

Without Kanter and Theis, the Celtics have Robert Williams and Vincent Poirier as options at center.

Thumbnail photo via Brad Rempel/USA TODAY Sports Images