Robert Williams could return to Celtics as soon as Game 3 Saturday

Robert Williams averaged 2.2 blocks and 9.6 rebounds a game this season.Matthew J Lee/Globe staff

Celtics center Robert Williams, who has been sidelined since tearing the meniscus in his left knee March 27, could return as soon as Game 3 of the first-round series against the Nets Saturday, a league source confirmed.

Williams is expected to test his knee prior to the game, and if there are no issues, he could be cleared to return. The team listed him as questionable.

Williams underwent surgery March 30 and the team announced that he would be sidelined 4-6 weeks. This would put him slightly ahead of that timeline.

Coach Ime Udoka has insisted over the past two weeks that he did not expect Williams to return to face Brooklyn, but the Celtics tend to err on the side of caution when addressing returns from injuries.

“He’s jumped up his level of activity as far as rehab,” Udoka said Thursday. “Being out there with some three-on-three, four-on-four, but not out there practicing with the team. You can’t really emulate the game, but he’s starting to do more contact work and getting out there as much as we can.

“There’s no need to put him out there for walk-throughs, so he’s doing things outside the group more so than with us.”

This season, the fourth-year big man averaged 10 points, 9.6 rebounds, and 2.2 blocks per game while emerging as a potential All-Defensive Team selection.

Williams likely will be on a minutes restriction when he returns. Daniel Theis has started both playoff games in his place, averaging 9.5 points and 6 rebounds, and helping the Celtics push to a 2-0 lead in this best-of-seven series.

The Nets could soon get some reinforcements, too, with point guard Ben Simmons in position to make his season debut in Game 4. Simmons, a three-time All-Star who was acquired from the 76ers in February, has been sidelined since last season’s playoffs because of mental health matters and a back issue.