The two-time All-Star had a lousy game against the Orlando Magic on Friday, tallying just four points, but he was back on it as the Bulls snatched a 121-107 victory over Boston.
Zach Lavine was five-of-10 on three-pointers for his 22 points, but it was his all-round effort that most impressed Bulls coach Billy Donovan.
The Celtic were on a nine-game roll, but they were no match for the Bulls on Monday.
LaVine said: "We've lost a lot in a row and they've won a lot in a row. I think we're a really good team, but we go through little lapses or times where we play bad. That's how fast the game can change."
He said of his sorry showing against Orlando: "Everybody has a career-worst night. I guess that was my night."
Coach Donovan commended the 27-year-old for putting the misfiring Magic game to the back of his mind, and refocusing.
Donovan said of LaVine: "I thought he played a great game tonight. I've got an enormous amount of confidence in his offense, in his ability to shoot the ball. He's done that his entire career, he's a lead at it.
"That will come back as he continues to play, and we're doing something differently offensively that he's having to work through, get accustomed to.
"There's a lot of things he can do to impact a game. Even though I think he missed his first three shots, it's probably not going to show up on the stats sheets but he generated a lot of open shots for our guys.
"He didn't shoot the ball at the percentage rate that he normally does, but I'm not worried about it.
"I thought his fingerprints were all over the game in a lot of different ways. He still got 22 points, but he did it defensively, he did it with his passing, he tried to get in there and rebound, he made good decisions.
"I thought he did a lot of extremely positive things."
DeMar DeRozan led the Bulls with 28 points on 11-of-24 shooting, hitting all three of his long-range attempts.