How Joe Mazzulla, Jayson Tatum, and Jaylen Brown spearheaded a massive Celtics comeback win

PHILADELPHIA — After Derrick White smoked a layup — and Guershon Yabusele sunk yet another three-pointer — it appeared that the Celtics’ were inching toward one of their worst losses of the season.

A 26-point deficit against the shorthanded 76ers loomed with three minutes left in the third quarter.

And, as many Celtics’ fans in attendance at Wells Fargo Aces began to warily look toward the exits, Joe Mazzulla also began to wonder if it was time to wave the white flag.

In fact, the third-year head coach challenged his players at halftime to up their energy — or he’d turn to the bench.

“Joe was like, ‘Yo, if you tired, just tell me, I can sit you guys down, let the Stay Ready guys play,’”…