The Boston Celtics' 2026 playoff run ended in stunning fashion—a 3-1 series lead against the Philadelphia 76ers evaporated in a heartbreaking Game 7 loss on Sunday night in Boston. For fans, the collapse was déjà vu, and for longtime Celtics loyalist Bill Simmons, the blame falls squarely on one person: head coach Joe Mazzulla.

On his podcast, Simmons—known for wearing his Boston sports heart on his sleeve—didn't hold back. "I thought Mazzulla was incredible in the regular season. Honestly, I voted for him for Coach of the Year," Simmons said. "But I don't know what they were thinking this playoffs. I have so many questions."

Simmons zeroed in on Mazzulla's rotation decisions, especially after Jayson Tatum's return from an Achilles injury. The Celtics had thrived during the regular season with a deep bench and an up-tempo style. But in the playoffs, Mazzulla shifted gears, slowing the pace and relying heavily on starters. "They went back to their 2024 style without the same players," Simmons argued. "They gave up on their bench. They didn't play with pace."

The most head-scratching move came in Game 7 itself. Mazzulla started Luka Garza, Baylor Scheierman, and Ron Harper Jr.—a trio that combined for 35 minutes but scored zero points. Harper and Garza each played fewer than ten minutes, a puzzling choice for a win-or-go-home game. "Did Philly win this series or did Boston blow it?" Simmons asked. "The answer is both. But I really think Mazzulla screwed this series up, and I'm always going to think that."

For a Celtics team that entered the postseason as a top contender, the early exit stings. And for Simmons, the memory of a blown 3-1 lead will linger—along with the questions about whether Mazzulla's adjustments cost Boston a shot at the title.