BOSTON — The Celtics now control their own fate in their quest to secure the Eastern Conference’s top playoff seed.

Isaiah Thomas scored 27 points to help Boston beat back a fourth-quarter charge and defeat the Brooklyn Nets 114-105 on Monday night.

The win clinched the Atlantic Division title and no worse than the No. 2 seed for the Celtics. More importantly, with Cleveland’s overtime loss at Miami on Monday night, a Boston win in its regular-season finale against Milwaukee on Wednesday or a Cleveland loss against Toronto would give the Celtics the No. 1 seed.

But if Boston loses to the Bucks and Cleveland beats Toronto, the Cavs would own the tiebreaker by virtue of their 3-1 head-to-head record with Boston.

Thomas said being in this position “means a lot.”

“It says a lot about this team,” Thomas said. “We’ve been through ups and downs. … We just kept going. That says a lot about who we are.”

After Monday’s win, several players gathered in the trainer’s room to watch the end of Cleveland’s game with Miami. When the Cavs tied it late in OT on Deron Williams’ 3-pointer before he completed the four-point play to put them up one, screams could be heard from inside. Clapping was heard again from the same room when the Heat finished their victory.

Al Horford had 19 points and eight rebounds for the Celtics. Avery Bradley finished with 18 points and five rebounds.

“It shows that we’re starting to play the right way,” Bradley said.

Brooklyn trailed by 27 in the third quarter before getting back into the game with a 12-0 run.

The Nets got as close as six in the fourth, but Thomas and Horford combined for 15 points in the quarter to help secure the victory.

Jeremy Lin led the Nets with 26 points and 12 rebounds. Brook Lopez finished with 25 points and passed Buck Williams to become the franchise’s career leading scorer.

Playing on a day’s rest following its win at Charlotte on Saturday, Boston led by as many as 21 in the first half.

Brooklyn also had a day off after Saturday’s one-point victory over Chicago, but couldn’t find the basket early on. The Nets missed 17 of their first 20 shots and shot just 27 percent in the opening 24 minutes.