How Joe Mazzulla's bold decision to start Robert Williams saved Celtics' season

Forsberg: How Mazzulla's bold lineup change saved the Celtics' season originally appeared on NBC Sports Boston

PHILADELPHIA -- The decision hit the Boston Celtics like a much-needed jolt of lightning.

With his team’s season on the brink, first-year coach Joe Mazzulla informed his players on the eve of Game 6 in Philadelphia that Robert Williams III would be shuffled back into the starting lineup.

A team reeling from an embarrassing Game 5 loss on its home court -- one that left the Celtics on the brink of an impossibly early playoff exit -- suddenly bubbled with energy.

"I was ecstatic about it," said Marcus Smart. "To be able to have Rob in there, he changes the game a lot."

With the lineup swap, Mazzulla essentially decided that if this ship was going down, it was going down with the group that had sailed the Celtics to a 2022 NBA Finals berth. It was going down with the core group that had distinguished Boston during its title quest a season ago.

With Williams III looking much more like the difference-maker he was last season, the Celtics bottled up Philadelphia’s offense with a dominant stretch to start Game 6, then leaned heavily into that defense all the way to the finish line of a 95-86 triumph at Wells Fargo Center.

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The lineup swap helped tied tie this series at 3-3; a winner-take-all Game 7 looms Sunday at TD Garden.

Williams III’s impact was undeniable. The Celtics posted a sizzling +31 net rating in Time Lord’s 28 minutes of floor time. That included a 74.1 defensive rating that was 15.5 points better than Boston’s already-stingy 89.6 mark for the game.

The double-big pairing allowed Al Horford to lean a bit more into the challenge of defending Joel Embiid, while Philadelphia guards were far more reluctant to attack the basket with Williams III in free safety mode.

"He’s the kind of guy that brings a level of joy to his teammates and a level of defensive -- I don’t know -- just support, to where the guys can be a little more aggressive, where guys can gamble a little bit, or just play the game," Mazzulla said of Williams III. "He does a great job of communicating, does a great job of just giving us that length and athleticism.

"I thought he was huge tonight."

Tomase: If we know these Celtics, Game 7 is about to be excruciating

For much of the 2022-23 season, Mazzulla had resisted the urge to reunite last year’s starting group. Boston’s so-called "preferred five" made it even easier for him by not playing anywhere near the level they showed last season. What’s more, Derrick White thrived in a starting role, often serving as Boston’s third most impactful player this season.

In 81 non-garbage-time minutes together, that group of Williams III with the core players had a minus-17 net rating, including an impossibly high 123.7 defensive rating. It was baffling considering the success of that group last season as Boston emerged as a second-half steamroller.

Mazzulla kept the double big pairing in his pocket for much of the Sixers series. The Williams III/Horford combo had played just seven minutes together entering Game 6. But White had struggled against Philadelphia’s size, limiting his defensive impact and contributing to his shooting struggles.

Mazzulla could have crossed his fingers that Boston’s shooting luck would flip after a dreadful night in Game 5. But he wasn’t leaving anything to chance.

Williams III’s impact was obvious from the jump. His presence made Philly drivers like James Harden and Tyrese Maxey think harder about dashes to the rim. Shots got tougher with Williams III, content to cheat away from PJ Tucker, sprinting all over the floor to contest anything he could get his long arms near.

Boston ultimately produced its most dominant defensive performance of the postseason. Yes, Jayson Tatum carried the team to the finish line after finding his milk-carton shot in crunch time. But the potential of having Williams III back to reestablish Boston’s defensive identity is what really had players rejuvenated in the aftermath.

"It made a tremendous difference. It don't take a professional to see the difference that Rob makes," said Jaylen Brown. "You put him similar in that role he played last year, where he can trust his instincts, make plays, even him tipping the ball out on rebounds and stuff like that. I feel like Rob felt a lot more comfortable out there in that double big (lineup)."

Added Smart: "Being able to have a lob threat, a rim threat, to be able to protect the rim on the other end. He’s huge for us. And I was proud to have him on the court. And that just goes to show you Joe’s learning just like all of us.

"I know he’s been killed a lot, rightfully so. He needs to make some adjustments and he did that. And that's all you can ask for. Just continue to be the best he can be. And it takes everybody. It’s a full-team effort."

Mazzulla had been under fire for Boston’s late-game woes in kicking away Game 4 in Philadelphia, and for not having his team ready to go in a listless Game 5. A coach who tends to stick to his guns (timeouts be damned), Mazzulla made a change that would have only brought more scrutiny if it fizzled.

Instead, he was rewarded with a momentum-shifting win that had the Celtics reinvigorated as the team trekked back to Boston with hopes of extending its title quest.

"In his first year, [Mazzulla has] done an unbelievable job. I know there's a lot of questions and doubts," said Tatum. "I told him a lot of times like, 'Yo, I got you. I got your back. We in this together.' I love that relationship that me and Joe have."

Tatum will dominate the headlines after shaking his shooting slump just in time to bury the Sixers in crunch time. But the Celtics' role players -- and their coach -- deserve the spotlight after Game 6.

Smart was fantastic, harnessing some of the heat he took after some near misses at the end of Game 4, to steady and direct the Celtics throughout Game 6. Malcolm Brogdon provided a first-quarter offensive spark as Tatum and Brown were struggling. White, as usual, didn’t let the shift to a bench role impact his play and had a solid night, too.

Smart timing

Boston outscored Philly by 22 points when Smart and Williams III were on the floor together in Game 6.

+22

Variation

Single

Mazzulla pushed the right buttons and the Celtics thrived whenever the Smart/Williams III combo was on the floor. Boston outscored Philadelphia by 22 in the 26.4 minutes that the defensive combo of Smart and Williams III were together. Philadelphia shot just 33.3 percent (15 of 45) in that span.

"Rob's presence, even if he's not blocking shots, his presence contesting shots, altering shots, that makes a difference," said Tatum. "His activity, getting offensive rebounds, having a lob threat out there. Rob played big today."

The Sixers tried to disrupt Boston’s change by leaning heavier on Georges Niang, who has shot the 3-pointer more consistently than Tucker in this series. But Williams III simply had the Celtics tapping into a defensive energy that brought back shades of last year’s playoff run when that was Boston’s calling card.

The question moving forward is whether the Celtics can harness that energy, or whether that starting group will revert to some of its regular-season struggles. It didn’t always feel like the Sixers were an ideal Williams III matchup and the Celtics have done their best to limit his time solo on the floor against Embiid. But it’s undeniable how different Boston’s defensive intensity was, particularly at the start of the game, knowing Williams III was back at free safety.

The change might have saved their season. It might have reopened the path to a chance to play for a title.

In the biggest moment of the season, the Celtics went back to what worked. It might just be the key to getting them where they ultimately want to go.