Joe Mazzulla remains noncommittal about starting Robert Williams, but Celtics big man might be forcing coach’s hand

Robert Williams is doing too much on both ends to keep him on the bench.Barry Chin/Globe Staff

Joe Mazzulla has a decision to make in the coming weeks. Robert Williams is getting up to speed after knee surgery and needs more minutes. Al Horford is wearing down and needs a break.

Mazzulla ended Saturday’s win over San Antonio with a two-big man lineup on key defensive stops, and later said he was curious how that unit would fare in a close game. The result was a crucial stand sparked by Williams and an important tap-back rebound by Horford to give the Celtics the last possession.

Williams is the key to the Celtics’ long-term success and everyone in the organization knows that; that’s why he has been handled so carefully. Williams has not proven durable, with two knee procedures in the past nine months and the knee still occasionally causing discomfort.

But with such a tantalizing player to watch, who makes such an impact on the game, there are always going to be calls for more playing time.

The Celtics increased Williams’s playing time last season, giving him nearly 30 minutes per game in his 61 starts, before he needed knee surgery and was limited to 23.2 minutes in the postseason.

He’s at 19.4 minutes per game in nine appearances this season. In that span, his offensive rating — the Celtics’ points per 100 possessions when he’s on the floor — is a career-high 119.7. His defensive rating is 108.9. The Celtics defensive rating overall is 111.1, ninth in the NBA, and giving Williams more playing time should only improve that number.

Considering his unquestioned impact, Williams is deserving of more playing time although it may require an occasional day off. Williams did not play in the Jan. 3 loss to the Thunder and responded with two sparkling defensive performances in Dallas and San Antonio.

Williams was a starter in all 61 appearances last season. But he’s come off the bench in 2022-23, with Mazzulla using Derrick White or Grant Williams to give the Celtics different looks. But it may be time for Mazzulla to opt for Robert Williams to begin games to give the Celtics more defensive energy and presence.

Williams displayed his impact on a second-period blocked shot on San Antonio’s Malaki Branham, who attempted a 3-pointer as Williams approached. That didn’t work out. Williams blocked the shot, gathered the ball, dribbled down the floor, and finished with a finger roll. The Celtics bench cheered in awe and delight.

This Robert Williams III block 😳

Celtics lead the Spurs 68-57 at halftime.

📲 https://t.co/1pomQZMAZK pic.twitter.com/yL6q3xP3lG

— NBA (@NBA) January 8, 2023

“Robert is special,” forward Jayson Tatum said. “It’s not many people in the league that can do the things he can do, affect the game the way that he can; and [as] his stamina gets better and he plays more games, he’ll make more plays like that and we’ll be a better team because of that.”

With 8:21 left in the game, Williams was replaced by Horford and Tatum asked if he was still on a minutes restriction. Williams said no.

Tatum told him, “get your [expletive] back in the game.”

“Whether he starts or comes off the bench, just want him on the floor, want him healthy,” Tatum said. “Want to be on the floor with him at the same time as much as possible. I’m going to start, so I’d like Rob to start. But whatever is best for the team, he’ll do that.”

When asked if he noticed opposing players avoiding him when he lurks in the paint, Williams said: “Yeah, a little bit. Just try to bring that same energy. That’s a big game changer for us, energy shifting. So I try to assert that as much as I can.”

Williams said he has embraced his bench role but he’s ready for more minutes. He pulled down six rebounds and blocked two shots in 6:44 of fourth-quarter time against the Spurs.

“Coming off the bench I feel like I’ve been able to be decisive on when we need to assert energy,” he said. “Just watching everything. Whether it’s starting or [off the] bench, I’m in.

“I’m here for whatever. Obviously they’re trying to be careful, making the smart decision and with the guys out there rolling, they’re rolling. [Whether] it’s 12 [minutes] or it’s 30, I’m in.”

Mazzulla won’t commit to putting Williams back in the starting lineup as the questions persist. Williams is one of the most impactful defensive players in the league, a potential Defensive Player of the Year candidate if he could play normal starters’ minutes over 70-plus games.

His impact is two-way: with the shot clock winding down in the final minute of the fourth quarter Saturday, White spotted him and desperately heaved an alley-oop that Williams caught and finished easily. No one else on the Celtics roster can make that play.

“Robert is special on both ends and it’s nice to have him back,” White said. “It adds a different element to our team.”

Mazzulla has to make a decision on Williams soon. Eventually, the Celtics are going to have to unleash Williams and see how his body reacts to the increased workload.

He says he’s ready.