Celtics center Robert Williams III has a torn meniscus and could miss six to eight weeks. Charles Krupa/Associated Press

BOSTON — Boston Celtics center Robert Williams III has torn cartilage in his left knee that will require surgery, likely keeping him out for the rest of the regular season and well into the playoffs.

Coach Ime Udoka said before Monday night’s game against the Toronto Raptors that a scan confirmed Williams will need an operation on a torn lateral meniscus. The player and team were still exploring options on what kind of surgery, and that would determine whether he is able to return should the Celtics embark on an extended playoff run.

“Everybody has to hold things down until he comes back,” Udoka said. “We have some optimism that hopefully he can come back.”

Williams was averaging 10 points, 9.6 rebounds and just over two blocks this season for the Celtics, who won for the 24th time in 28 games on Sunday to take over the top spot in the Eastern Conference. He left the 134-112 victory at the end of the third quarter after scoring 10 points with 13 rebounds.

Udoka said after the game that Williams had “quite a bit of pain.”

A day later, the team announced that he had a torn lateral meniscus but provided no timetable for his return; the injury usually takes a minimum of 6 to 8 weeks for recovery, which would keep him out through the conference finals.

“There are some (operations) that keep you out longer than others,” Udoka said on Monday. “We’re hoping for the best.”

The Celtics were also without big man Al Horford due to unspecified personal reasons. Jayson Tatum and Jaylen Brown were also out for Monday night’s game in Toronto because of sore knees.