Watch: Cavaliers storm back in third quarter to close deficit vs. Celtics

Evan Mobley capped Cleveland's run by fighting for two offensive rebounds and eventually dunking to cut Boston's lead to six points. Mobley had 14 points in the quarter, part of his team-high 22 points.

The Celtics continued to light it up from deep in the third quarter, going 5-for-10 from three-point range, but Cleveland countered by going 13-for-19 on two-pointers, on their way to a 40-point quarter.

It was exactly the counter Cleveland needed against the hot-shooting Celtics, who were deadly offensively but undersized on defense. They did go 3-for-6 from three-point range in the quarter, but the comeback was fueled by layups and dunks.

Cleveland eventually cut the lead to two points on a Jarrett Allen layup, but Jayson Tatum came up big with a buzzer-beater. With less than a second remaining, Tatum dropped Georges Niang with the help of a little push off, and sank his sixth three-pointer of the game to pad Boston's lead going into the deciding quarter.

Boston was dominating for the first 30 minutes, but the third quarter showed why the Cavaliers have managed the second-best start in NBA history this season. Through three quarters, no one is backing down.