On Tuesday, May 26, Boston Celtics head coach Joe Mazzulla became the youngest NBA Coach of the Year winner since Phil Johnson in 1975.
At just 37 years old, Mazzulla has already built a decorated resume. In 2024, he became the youngest head coach to win the Finals since player-coach Bill Russell in 1969. Mazzulla also has the highest regular-season winning percentage in NBA history at 72.6%.
Given those remarkable achievements from just four seasons, Mazzulla’s job security should be unquestioned. Yet after multiple disappointing playoff exits, lingering doubts remain about whether he is the right coach to maximize the championship window of Jayson Tatum and Jaylen Brown‘s primes.
Gap Year Overachieving Not Enough?
Stop me if you’ve heard this before: Mazzulla will enter next season under close watch.
After Boston’s devastating playoff exit in 2025 — a second-round loss to the rival New York Knicks that also saw Tatum suffer a torn Achilles — the Celtics stripped down their roster and payroll. Several Hall of Fame-level contributors departed, and with Tatum expected to miss the entire 2025-26 season, Mazzulla suddenly had an opportunity to prove himself without overwhelming star talent.
A 56-win season in a transition year where expectations were modest should have silenced the criticism. Instead, it only complicated the conversation.
Mazzulla’s Coach of the Year campaign featured innovation, player development, and dramatic in-season improvement.
However, Boston’s third disappointing playoff exit in four seasons — particularly after blowing a 3-1 series lead to the Philadelphia 76ers — reignited concerns about his adaptability in the postseason.
In almost any other context, a championship and historic regular-season success across four years would represent an unquestioned success story.
But the standard surrounding the Celtics is different. With two homegrown superstars in their primes, the bar for success is high. The lows of Mazzulla’s tenure have been impossible to ignore.
Playoff Shortcomings
Mazzulla’s Celtics have taken the “championship or bust” idea to heart.
Their 2024 playoff run was one of the most dominant in NBA history. Since the league adopted its current four-round, best-of-seven playoff format, only two teams have lost three or fewer games during a championship run: the 2024 Celtics and the 2017 Golden State Warriors. Boston won 10 consecutive playoff games on its way to the Finals and never trailed in a series.
Winning a championship at such a young age is an extraordinary accomplishment for Mazzulla. Two years later, at 37, Mazzulla is the same age as Hall of Fame coach Pat Riley was when Riley won his first of five championships.
At the same time, failing to win a championship with a roster as talented as the 2024 core would have been viewed as a massive disappointment. And outside that championship season, the Celtics have repeatedly fallen short in series in which they entered as overwhelming favorites.
Sources for series odds in 2023, 2025, and 2026
Difference Between Regular Season and Playoff Coaching
Mazzulla has consistently proven himself to be an elite regular-season coach.
The NBA’s 82-game regular season can be grueling, especially for teams with championship aspirations. Maintaining urgency for seven straight months can be difficult when everyone understands the true evaluation begins in April.
With Boston’s pedigree as a championship contender, they could have plummeted this season with the baked-in excuses. Instead, they played with relentless energy and focus. The team’s buy-in to Mazzulla’s system never wavered, even as he constantly tinkered with minutes and roles across the roster.
Even in previous years when the Celtics had greater collective roster talent, their consistency never lapsed. During the 2024-25 season, Boston clinched the Eastern Conference’s No. 1 seed with 11 games remaining despite missing a combined 81 games from Brown, Al Horford, and Kristaps Porziņģis.
Mazzulla’s offensive philosophies have been devastating over the course of 82-game regular seasons. Without the do-or-die nature of the playoffs, the math behind high-volume, high-quality three-point looks is a problem opposing teams haven’t found an answer for.
However, in a seven-game series, the Celtics can’t afford to be so patient in their process. Shooting variance becomes magnified in the playoffs.
Poor shooting luck has haunted Boston in its past two playoff exits, but the inability to find a counterpunch is not an excuse. Mazzulla’s lack of adjustments has become a weak point.
What Are the Adjustments?
This season’s roster featured a wide range of complementary skill sets from a rotation as deep as Mazzulla has had yet. But for all of the innovation during the regular season, the Celtics went down without much creativity.
Rotations shrink in the playoffs as the margin for error decreases. Still, in 48-minute games when the Celtics’ process looked gummed up, Mazzulla could’ve leaned more on chaos-causers like Jordan Walsh, Hugo González, or Ron Harper Jr., even for short stints to help energize the team. Or even in Game 5 when Boston’s offense scored just 11 points in the fourth quarter and Payton Pritchard, who is a proven offensive performer, watched from the sidelines until the game was all but over.
Beyond the center rotation, which was a losing equation for the Celtics regardless of how Mazzulla deployed it, the lineup innovation that made the regular season so special was gone. That was, until Game 7, when he threw out a starting lineup that played zero minutes together all season.
Learning Lessons
Ahead of the 2022-23 season, when Mazzulla took over as Celtics interim head coach, Boston had made the playoffs in the previous eight seasons. With Tatum and Brown ascending to perennial All-NBA talents, surrounded by several other high-level contributors, Mazzulla was the one in the locker room who needed the most development.
Mazzulla is still young and clearly has a phenomenal feel for the modern game of basketball. The clock is ticking for Mazzulla to figure it out, though. Tatum and Brown are too talented to waste their primes on a hypothetical great coach.
If he can improve his feel for postseason adjustments, the Celtics have a stellar combination of basketball minds in Mazzulla and Brad Stevens, their president of basketball operations, for years to come.
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