The Boston Celtics learned a hard lesson in the first round of the NBA playoffs: never underestimate the impact of a healthy superstar. What started as a seemingly straightforward series against the Philadelphia 76ers turned into a grueling seven-game battle, and according to the Celtics, there's one clear reason why.

After jumping out to a commanding lead, Boston looked every bit the favorite. They crushed the Sixers 123-91 in Game 1 and took Game 3 by eight points, outscoring Philadelphia 328 to 302 through the first three contests. It seemed like the Celtics were cruising toward an easy series win.

But then, everything changed.

"What changed in the series was Joel Embiid came back," Celtics head coach Joe Mazzulla said bluntly. "They're a completely different team."

Embiid, the former MVP and one of the most dominant forces in the game, had been sidelined to start the series. His return in Game 4 didn't immediately flip the script—Boston actually won that game—but it set the stage for a dramatic shift in momentum. Over his four appearances in the opening round, Embiid dropped more than 30 points twice, providing the kind of clutch scoring and defensive presence that can turn a series on its head.

Boston's big man Neemias Queta, who drew the unenviable assignment of guarding Embiid throughout the series, echoed his coach's sentiments. "They're a totally different team with him," Queta explained. "Great player, makes a lot of plays, makes it hard for every player on the court. Whether you double him or try to be more aggressive, he changes everything."

For the seventh-seeded Sixers, Embiid's return was the spark they needed to pull off the upset and advance to the semifinals. For the Celtics, it was a painful reminder that in the playoffs, one player's presence can make all the difference between an early exit and a deep run.