Easy to forget Celtics’ red-hot start has happened without Robert Williams

The Celtics will be even stronger when Robert Williams returns to game action.Jim Davis/Globe Staff

CHICAGO — The Celtics are in the midst of an impressive nine-game winning streak that has given them the best record in the NBA, and it’s easy to forget they’re doing this without one of their most essential players.

Center Robert Williams has been sidelined since undergoing a maintenance surgery on his left knee Sept. 23. At the time, the team announced he would resume basketball activities in 8-12 weeks.

Williams reached the eight-week mark last Thursday, and on Sunday coach Joe Mazzulla said Williams is doing 2-on-2 and 3-on-3 workouts with members of the coaching staff. When Williams does come back, Mazzulla said, he does not think Boston’s scorching start will be disturbed.

“I think we started off the season building our system on both ends of the floor with the full team in mind,” Mazzulla said. “So it’ll be a seamless transition, because everything we’re doing he has the ability to fit right in and help with on both ends of the floor.”

There is no set date for Williams’s return to full practices or games, but things certainly appear to be trending in that direction. Two weeks ago Williams revealed he had resumed running and dunking, and that the training staff was just trying to ensure that he did not do too much, too quickly.

“We’re happy with him as far as his progression and the work he’s put in toward coming back,” Mazzulla said. “He’s picking it up on the court a little bit . . . He looks good. He’s healthy and responding well to it. He’s in a good space as far as patience, and he’s doing the work he needs to do.”

Williams, a second-team All-Defense choice last season, tore the meniscus in his left knee in March and was sidelined for about a month after surgery before returning midway through the opening-round playoff series against the Nets. He often appeared hobbled during the postseason, but the Celtics were confident that he just needed an offseason of rest to return to form.

Then some pain returned as he ramped up workouts leading up to training camp in September, and he elected to have the latest surgery. Even though it appeared to be a significant setback for the Celtics, the team has rolled on without him thanks in large part to its top-ranked offense that is built around filling the court with 3-point shooters.

“People don’t understand how valuable and important Rob is to our team and our success,” Celtics forward Jayson Tatum said. “He doesn’t score a lot of points, but just his presence on both ends makes us that much better. It’s kind of damn-near impressive what we’re doing without Rob.”

The Celtics are certain Williams’s return will raise their ceiling. Although Williams rarely shoots from the perimeter, he is an excellent passer and a devastating lob threat. His defensive impact as a rim protector is even more obvious.

“He’ll help our spacing on the offensive end,” Mazzulla said, “and then defensively we’re doing a great job of our individual defense and our shift activities, and he’ll fit right in as far as our rim protection. So, both systems were built for our full team, so when we get that it’ll be a seamless transition.”

Mazzulla said he is also eager to see the emotional boost that Williams’s return should provide.

“I think just the camaraderie,” he said. “The guys really like playing with each other, and when guys are out they’re very supportive of each other when they come back. So, they’re really excited to have a full team. I see that in them.”

***

Mazzulla said guard Marcus Smart, who missed the last two games because of swelling in his right ankle, completed a shooting workout Sunday morning and is “progressing really well” ahead of Monday’s game against the Bulls. Guard Malcolm Brogdon, who returned Friday after missing four games with hamstring tightness, made it through the Pelicans game with no issues.