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 No2 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 would give the Celtics the No1 seed.

But if Boston lose to the Bucks and Cleveland win their finale against Toronto, the Cavs would own the tiebreaker by virtue of their 3-1 head-to-head record with Boston. The Cavalier’s loss to Miami was their third in a row as form deserts them as the playoffs loom.

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’ three before he completed 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, cementing the Celtics’ chance to claim top seed Wednesday.

Al Horford added 19 points and eight rebounds. 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 an 18-5 run got it back into the game. The Nets got as close as six in the fourth, but Thomas and Horford combined for 15 points in the period 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 with a jumper late in the fourth quarter.

Playing on a day’s rest following their win at Charlotte on Saturday, Boston led by as many as 21 in the first half. Brooklyn also had a day off coming off 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% in the opening 24 minutes.