BOSTON — The Boston Celtics have had more time than usual to reflect on what went wrong during the playoffs. A little over five months ago, the Celtics' quest to capture back-to-back titles was cut short during the Eastern Conference Semifinals, as they fell in six games to the New York Knicks — suffering their earliest postseason exit since 2021. Celtics star Jaylen Brown used that extra time off to learn from his team's past mistakes, and he enlisted some unlikely help to do so.

At practice on Monday afternoon, Celtics head coach Joe Mazzulla and Celtics star Jayson Tatum could be seen talking to ex-Knicks coach Tom Thibodeau. Although Thibodeau is a New England native and was once an associate head coach with the C's, he was Boston's sworn enemy in May. However, the Knicks fired Thibodeau in June despite the fact that he led them to their first Eastern Conference Finals appearance in 25 years.

With Thibodeau out of a job, he's free to share his basketball expertise with the rest of the NBA. Mazzulla, Tatum, and especially Brown, clearly relished that fact.

“I thought that was awesome,” Brown said about having Thibodeau at practice. “Obviously [the Knicks] eliminated us last year and him being able to kind of give us some of the thoughts that he saw in that series, and some of the stuff that they broke down in our personnel and even in our team, helps us grow and learn from that.”

Mazzulla has long respected Thibodeau, so it's no surprise he got the invite to the Auerbach Center. Thibs' situation is a bit unusual though, as few coaches are let go after helping their team win a second-round series they were largely not favored to prevail in.

“This was a unique position,” Brown admitted. “A guy can come in and directly give us some feedback on how we can be better, I can be better. So, I value that. That was great.”

Why Tom Thibodeau's presence at Celtics practice was a unique occurrence

Before the 2024-25 Knicks, the last two squads to triumph over the Celtics in the playoffs were the Golden State Warriors and Miami Heat, two perennial playoff teams who still employ the same coaches years later. New York is the outlier here, and Boston wants to use that to its advantage.

“To have Thibs here at our practice and explaining some of the things that he saw to help them beat us only helps me get better,” Brown said.

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But, how did Thibodeau actually help the C's?

While Brown didn't delve to deep into the details, he did say that the former Knick talked over film — presumably from the Eastern Conference Semifinals — with the Celtics. In addition, Thibodeau discussed how he specifically schemed against Tatum and Brown on defense, which could certainly be valuable information for the latter, who is preparing to enter his 10th year in the Association on Wednesday.

“He's breaking down some film and stuff like that,” Brown described. “Talking to Joe from a team perspective and like from a top-down perspective of what he wanted to do with me and Jayson or what he wanted to do when the ball was in my hands.”

While Brown might have heard some things from Thibodeau that he might not have enjoyed since he's still admittedly bitter about losing to the Knicks, the 2024 NBA Finals MVP understands that learning how an opponent thinks and plans against you is crucial, especially when the lessons are coming directly from the source.

“It allows you to grow,” Brown said of Thibodeau's teachings. “If you're humble enough to listen, it'll allow you to grow.”

Alongside Thibodeau, 2025 WNBA Coach of the Year Natalie Nakase attended Celtics practice as well on Monday. This wasn't the Golden State Valkyries skipper's first time at the Auerbach Center either, emphasizing how Mazzulla is eager to take in as many basketball perspectives as he can from inside and outside the NBA.

When the 2025-26 campaign finally starts for the Celtics on Wednesday night with a home opener against the Philadelphia 76ers, perhaps Mazzulla, Brown, and the rest of the Green Team can show what they've learned and, most importantly, demonstrate improvement and resolve in the face of an uncertain season.