Jayson Tatum corralled a rebound late in the third quarter, dribbled up court and had the matchup he wanted. With De’Anthony Melton guarding him, Tatum took a few steps back to size up his defender.

There was almost no doubt how this possession would end.

Tatum took a few dribbles and went to work. He crossed over between his legs a few times. He took a step to his left and unleashed another 3-pointer. Swish.

Upon draining yet another shot on a day full of them, Tatum turned to where his mom and son Deuce typically sit courtside and posed a one-word question.

“What?”

There wasn’t much else to say. On one of the biggest stages of his basketball life, Tatum delivered the best game of his career and one of the greatest in Celtics playoff history. Tatum scored 51 points – an NBA Game 7 record – with 13 rebounds and five assists to lead the Celtics to a blowout 112-88 victory to dispatch the Philadelphia 76ers and advance to the Eastern Conference Finals once again.

Game 1 against the Miami Heat is on Wednesday night at TD Garden.

The Celtics were in a 3-2 series hole and it had been a mostly frustrating series for Tatum, who struggled for long stretches of the first six games of this series. But he delivered when the Celtics needed their superstar most. He erupted for 16 points in the fourth quarter to will the Celtics to a Game 6 win in Philadelphia, then carried the momentum into an epic performance on Sunday afternoon at a raucous TD Garden.