Boston Celtics center Robert Williams is progressing well after surgery on his torn meniscus, but Ime Udoka doesn’t expect him to be ready for the first round of the NBA Playoffs.

“We haven’t looked at him being here for the first round, honestly. A four to six (week) timeline is what it is,” said Udoka Wednesday before their game against the Bulls. “Everyone reacts differently to surgeries. But it’s possible. We haven’t really ruled him out if he’s ready, but we’re going in with the mindset that he won’t be here for the first round.”

Williams had surgery on March 30, and the Celtics have been able to win the two games they’ve been without him as they continue the push for the top seed in the Eastern Conference. If Boston gets a top seed, the result against a lower-tier team in the first round might not change much without Williams though.

The original timetable was four to six weeks, and it looks like it will stay that way, as Udoka said. The second round begins in late April/early May, which is roughly five weeks after his injury. If Williams is lucky, he could see time at the end of the first round if the two sides make it that far into the round.

Williams could have traveled with the team to Chicago and Milwaukee (against the Bucks Thursday) but the big man stayed in Boston to continue his rehab at the Red Auerbach Center.

“Although he could’ve done it here, he’s a guy who’s locked in with the guys, so we felt it was better to leave him there and get the process rolling as fast as possible,” Udoka said. “Like I said, he’s in good spirits, it’s his first surgery, so he’s attacking it with the right mindset and hoping to have him back sooner rather than later.”

In Williams’ absence, the team has relied a lot more on center Daniel Theis, who was acquired at the deadline and has stepped into a big role for the Celtics. Theis has 16 points across 53 minutes over the past two games.

“Another guy who can do some of the same things and obviously great insurance policy to have him there,” Udoka said of Theis. “A guy that’s been around, although different schematically. The guys all know him and know what he’s about, and he’s picked up pretty quickly. And so, valuable there. But Al is a guy that’s played on and off-ball all season so he’s pretty comfortable in either spot.”