After undergoing surgery for a torn meniscus in his left knee Wednesday morning, Boston Celtics center Robert Williams III is expected to return within four to six weeks -- a timetable that could land him back in the lineup as soon as the second round of the Eastern Conference playoffs, sources told ESPN.

Williams suffered the tear Sunday night, but the extent of the injury allowed for a procedure that won't require him to be sidelined for several months, sources said.

After the procedure on Wednesday, there was some initial optimism of a return on the shorter end of the timeline, sources told ESPN. The Eastern Conference semifinals are expected to start around May 1.

Boston (47-29) is currently third in the Eastern Conference with six games left in the regular season -- only one game out of first place.

Williams has been an immense part of the NBA's best defense and hottest team over the past two months. He is No. 1 among 169 players who've 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, $52 million extension in the offseason, has averaged 10 points, 9.6 rebounds and 2.2 blocks and is shooting 73.6% from the floor.