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Jaylen Brown of the Boston Celtics drives against Paul George of the Philadelphia 76ers during Game 5 of their first-round playoff series at TD Garden on April 28, 2026.

The Boston Celtics were 12 minutes away from ending this series.

Instead, they’re headed back to Philadelphia with the series suddenly feeling very different.

After a Game 5 collapse at home, the Celtics failed to close out the Philadelphia 76ers and now face a pivotal Game 6 on the road Thursday night — a scenario that didn’t seem likely just one quarter earlier.

Boston entered the fourth quarter in control, but everything unraveled late. Missed shots, empty possessions, and costly mistakes flipped the momentum — and the series.

Now, what looked like a routine closeout has turned into a high-pressure moment.

The team entered the playoff series as the clear favorites.

Joe Mazzulla Points to Costly Mistakes in Game 5

After the loss, Celtics head coach Joe Mazzulla didn’t overcomplicate what went wrong.

“Obviously had some back-to-back turnovers that led to 3s. We had some empty possessions on the offensive rebound that led to some of the shots there. I think the game is connected in that and I thought it was a little bit of both (bad offense and defense),” Mazzulla said.

The sequence he described defined the game’s turning point. Boston’s offensive execution slipped at the worst possible time, and those breakdowns immediately translated into scoring opportunities for Philadelphia.

Instead of controlling the pace and closing things out, the Celtics opened the door — and the 76ers took full advantage.

Mazzulla also downplayed the significance of the late-game stretch, at least outwardly.

“Got some good looks. Weren’t able to capitalize,” he added.

But the numbers tell a tougher story. Boston shot just 40.2% from the field and struggled to generate consistent offense when it mattered most — a sharp contrast from the level they’ll need in Game 6.

Momentum Has Shifted — and So Has the Pressure

GettyJoel Embiid of the Philadelphia 76ers reacts as Jayson Tatum of the Boston Celtics walks away during Game 5 of their first-round playoff series at TD Garden on April 28, 2026.

The biggest takeaway from Game 5 isn’t just the loss — it’s the shift in momentum.

Philadelphia now heads home with belief, while Boston faces the pressure of needing to respond in a hostile environment. Closeout games are never easy, but the Celtics had a golden opportunity to avoid this exact situation.

Now, instead of advancing, they’re being forced to prove they can regroup.

Game 6 becomes more than just another chance to win the series — it’s a test of composure.

Can Boston reset after letting one slip away?

What to Watch in Game 6

Game 6 tips off Thursday night in Philadelphia, where the 76ers will look to force a decisive Game 7.

For the Celtics, the path forward is clear.

They must clean up the turnovers that fueled Philadelphia’s run. They must convert on quality looks. And most importantly, they need to regain control in late-game situations — something that completely disappeared in Game 5.

Because if the same issues show up again, this series could quickly flip from expected victory to something far more dangerous.

Boston is still in control.

But after Game 5, it no longer feels comfortable.