Jason Glushon, Brown's agent, informed ESPN's Adrian Wojnarowski about the terms of the agreement. Yahoo Sports' Chris Haynes reported more contract details: "He can secure $8M in incentives if he wins MVP, DPOY or makes one of three All-NBA Teams. He pockets $4M if plays 65 or more games, team wins 49 or more games and reaches second round of playoffs. Total guaranteed salary $103M."
Brown, 22, was the No. 3 overall pick in the 2016 draft. He averaged 13.0 points and 4.2 rebounds on 46.5 percent shooting last season, disappointing those who expected him to have a big year in the wake of his breakout during the 2018 playoffs.
While Brown could become a two-way star in due time, he remains a developing player on a team that is looking to make a title push.
The Celtics have lauded Brown's improvement on defense in particular.
"He definitely has a lot on him. We know, and this coaching staff knows, his ability," Celtics guard Marcus Smart said about Brown in December 2017, per Chris Forsberg of ESPN. "And [Brown is] athletic enough to guard a lot of guys. So once he understands that and he takes that head-on, he'll be a better all-around player. And he's been doing a pretty good job so far."
According to Chris Haynes of Yahoo Sports, the Celtics initially offered Brown a four-year, $80 million extension, which he turned down. Negotiations continued up until the Oct. 21 deadline for rookie extensions, and the two sides came to a middle ground.
Brown isn't good enough to be considered a cornerstone of the Celtics, but he's still young and has flashed a ton of potential at times. He doesn't turn 23 until later this month, and his year-to-year improvement suggests an even bigger ceiling could be on the horizon.