BOSTON -- Miami coach Erik Spoelstra used to coach the Big Three with the Heat.

On Friday night, he was clobbered by the Little One.

Isaiah Thomas, generously listed at 5 feet 9 in your program, scored a club-record 29 of his career-high 52 points in the fourth quarter -- the highest total ever run up by a Boston guard -- and led the Celtics to a 117-114 victory over the undermanned Heat.

"That fourth quarter ... it just felt like I was out there by myself, working on my game in the gym," Thomas, Boston's Little Big Man, said after beating his previous high of 44, set just 10 days earlier.

"Throwing up everything and it was going in. It was a special feeling."

It was the fourth-highest scoring total in Celtics history, behind Larry Bird's 60 in 1985, Kevin McHale's 56 in 1985 and Bird's 53 in 1983.

Thomas, who outscored the entire Miami starting lineup 52-51, scored 29 of the Celtics' 35 points in the quarter, the last basket a three coming on a long bomb from well behind the 3-point line. He hit six 3-pointers in the quarter and finished 15 of 26 from the floor, 9 of 13 in the fourth, 9 of 13 from 3-point range and 13 of 13 from the foul line.

"I have to give credit to my teammates and coach Brad (Stevens)," Thomas said. "They were saying, 'o 60!'"

He was just two points off the NBA record, saying, "Yeah, that was crazy. I mean, to be in the same conversation as Wilt (Chamberlain), maybe one day ... "

Amazingly, Thomas, who came in averaging 6.3 assists per game, didn't have a single assist -- and heard chants of "M-V-P" from the home crowd in the latter stages of the game.

Bird (1983) and Darren Daye (1995) had held the club record with 24 points in a fourth quarter.

On Dec. 20 at Memphis, Thomas scored 36 of his 44 points after halftime in an overtime win. He has scored 20 or more points in all but one game this season (18 in that one) and has 20 or more in 18 straight, an NBA high.

Asked if he thinks he belongs in the conversation regarding the league's best scorers, Thomas said, "I do. The only reason I do is because I'm 5-9. They don't talk about me like they do all the other guys, but I'm fine with it."

Al Horford had 21 points and six rebounds as the Celtics (20-14) won for the seventh time in their last nine games -- and did it without No. 2 scorer and leading rebounder Avery Bradley, who was sick and not in the building.

The home team, predictably flat after an emotional loss in Cleveland on Thursday night, survived even though the Heat shot 62.8 percent from the floor in the second half.

"It was obviously an unbelievable effort to not only finish out a long month, but six games in nine days, come back, get in at three in the morning, and go for 29 in the fourth," Stevens said of Thomas. "It's remarkable. I mean, I don't know what else to say."

Thomas, in Boston's first 50-point game since Paul Pierce had 50 in a double-overtime game in 2006, tied the club record for 3-pointers.

The Heat, missing leading scorer Goran Dragic (back), lost their fourth straight and seventh in the last eight -- falling to 10-24 despite turning in a strong performance start to finish.

"That's what great players do on this league," Spoelstra said of Thomas. "He's one of the very best fourth quarter players in this league for that reason. He doesn't shy from the shot in the moment now. Inside half-court he feels like is within his rhythm. You have to play on him all the way out there.

"When somebody's shooting with that kind of confidence and freedom, it makes it very, very tough."

James Johnson led the Heat with 22 points, and Josh Richardson and Tyler Johnson scored 19 apiece. Big man Hassan Whiteside had 11 points and eight rebounds before leaving the game late after getting poked in an eye.

Wayne Ellington added 14 points and Justise Winslow, who was 0 of 9 from the floor on Thursday, had 11 points and nine rebounds in the loss.

The Celtics moved to 3-0 against the Heat this season.

NOTES: Miami G Goran Dragic was out for the second time in three games with back spasms and Boston G Avery Bradley was sick and out. Bradley hurt both hands in Cleveland on Thursday, but would have been able to play had it not been for illness. ... Miami C Hassan Whiteside had 17 rebounds in each of the two earlier games between the teams while Dragic scored 58 points in the two games, with 17 assists in one -- both losses. ... Dragic was just 2-for-11 from the floor in 32 minutes at Charlotte Thursday night. ... The Heat host the Detroit Pistons on Sunday night. The Celtics are off until Tuesday, when the Utah Jazz visit for Game 2 of a four-game homestand.