But Brown got the last laugh Wednesday night at TD Garden.
The 22-year-old guard -- who was a rookie in Thomas' final season in Boston in 2016-17 -- scored 22 points in Boston's 140-133 win over Washington.
Two of those points came against the 5-foot-9 Thomas on an isolation play that Brown seemed to relish.
When IT keeps talking trash about your haircut, you shoot two over him 🤔 pic.twitter.com/GorXYrN7jy— Celtics on NBC Sports Boston (@NBCSCeltics) November 14, 2019
When asked about the play after the game, Brown fired his return shot at I.T.
"Oh man, he knows. You don't need to say it. He knows he can't guard me," Brown said.
"He was screaming for help. Maybe his braids was too tight and he thought he could guard me."
Lest you think there's actually any bad blood here, that's just how Brown and Thomas interact. The 30-year-old guard acted as a mentor to Brown in that 2016-17 campaign, and that included plenty of good-natured banter.
"It's great to see him out there," Brown quickly followed up. "Me and I.T. joke back and forth, but I look at I.T. as like a big brother. He's a great teammate, great guy and I'm happy to see him out there playing well."
Thomas dropped a season-high 18 points on 7-of-14 shooting, tallying his first points at TD Garden since his trade to Cleveland in the 2017 offseason.
But Thomas' "little brother" still outscored him by tallying 20-plus points in his third consecutive game, as the Celtics moved to an NBA-best 9-1 on the season.
That's a good way to get even.
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Jaylen Brown gets revenge on ex-Celtic Isaiah Thomas with ruthless burn originally appeared on NBC Sports Boston