From the same article:
Brissett knows how the Pacers play. He understands their tendencies. He has played these guys in practice for years. This was the moment for him to show why the Celtics signed him.
and
Mazzulla has drilled the Celtics on every position, in every lineup, so they can step into these random matchups at the sprain of a wrist. After the second unit got torched early in Game 1, he was a big part of why the Celtics’ second unit went on a 17-0 run and seized control of the game.
“That’s something that Joe really likes,” Brissett said. “We play sometimes with two bigs or one or none, so everyone out there has to know every single position, whether you’re off the ball or in the action.
“We don’t know what they’re about to throw out, so we’ve gotta be prepared and ready.”
Evidently Jared Weiss hasn't realized that Joe is an idiot who doesn't do any coaching.
Banned temporarily for, among other sins, being "Extremely Deviant".