CLEVELAND – The Boston Celtics caught the Cleveland Cavaliers napping.

Trailing by 21 in the third quarter, Boston cut the deficit to five by the end of the quarter, tied the score on Marcus Smart’s three-pointer with 5:48 left in the fourth quarter and took the lead on Kelly Olynyk’s short one-handed jumper in the paint with 4:22 remaining.

Avery Bradley’s three-point shot, which hit the rim, bounced around and dropped in with 0.1 seconds left gave Boston a 111-108 victory Sunday in Game 3 of the Eastern Conference finals.

It was Cleveland’s first loss of the playoffs and ended its 13-game postseason winning streak dating to last year’s NBA Finals.

Game 4 is Tuesday in Cleveland (8:30 p.m. ET, TNT) with the Cavs up 2-1 in the series.

By far, it was Boston’s best game of the series, and not coincidentally, it was LeBron James’ worst. James had just 11 points (three in the second half) on 4-for-13 shooting, including 0-for-4 on three-pointers. He also had six rebounds, six assists and six turnovers.

“I had a tough game. Period. Not just in the second half,” James said. “Me personally, I didn’t have it. My teammates did a great job of keeping us in the game and building that lead, but me personally, I didn’t have it. That’s what I’ve got to say about my performance.”

Guard Marcus Smart led the Celtics with 27 points (7-for-10 from three) seven assists and five rebounds. Bradley added 20 points and forward Jae Crowder finished with 14 points and 11 rebounds.

Playing without All-Star guard Isaiah Thomas (injured right hip) who is out for the remainder of the playoffs, Boston didn’t quit in the face of a difficult situation. The Celtics lost the first two games in Boston by a combined 57 points.

“Our message is always to try to play the next possession as well as you possibly can,” Celtics coach Brad Stevens said before the game. “We never really get out of that. Our guys have done a good job of that all year. They’ve done a good job of staying positive after a tough situation.

“It’s a great testament to these guys. They are extremely resilient. They’re a pleasure to coach because there’s never any finger pointing. There’s never any of that stuff. It’s just, let’s figure out what we need to do to be on the attack and try to manage our margin for error better.”

The Celtics outscored the Cavs 61-42 in the second half.

Boston dealt with Cleveland’s 14 three-pointers in the first half and great games from Kevin Love (28 points, 10 rebounds), Kyrie Irving (29 points) and Tristan Thompson (18 points, 13 rebounds).

Follow USA TODAY Sports’ Jeff Zillgitt on Twitter @JeffZillgitt

PHOTOS: Best of the conference finals