Sources - Boston Celtics center Robert Williams has torn meniscus, out at least several weeks

Boston Celtics center Robert Williams III — an anchor of the league's best defense — suffered a meniscus tear in his left knee and will miss several weeks, minimally, sources told ESPN on Monday.

An MRI on Monday revealed the tear, and further evaluation Monday will help provide a timetable on a possible return, sources said.

Boston moved into first place in the Eastern Conference on Sunday, and Williams, 25, has been an immense part of a dominant league-best defense. Williams was injured in the 134-112 victory over the Minnesota Timberwolves on Sunday — the Celtics' 24th victory in 28 games.

Williams is No. 1 among 169 players in the league who have defended 500-plus shots as the closest defender, per Second Spectrum tracking. Only Williams has held opponents under 40% shooting.

Williams — who signed a new four-year, $54 million extension in the offseason — has averaged 10 points, 9.6 rebounds and 2.2 blocks. He has shot 73% from the floor.