Jose Calderon celebrates a basket during the Raptors' upset win in Boston on Wednesday. ((Winslow Townson/Associated Press))

Jose Calderon scored a team-high 24 points, including a go-ahead three-point play with 10.5 seconds left, as the Toronto Raptors upset the NBA-leading Celtics 114-112 on Wednesday night in Boston.

Calderon, who also dished out a game-high 13 assists, began his heroics by hitting a pair of clutch free throws with 31.3 seconds remaining to make it 111-110, giving Toronto its first lead since two minutes before the end of the fourth quarter.

Boston's Ray Allen answered by collecting a rebound near the top of the key and knocking down a jumper to put the Celtics back ahead with 14.9 seconds on the clock.

But Calderon took matters into his own hands again, driving strong to the hoop, drawing a foul from Paul Pierce and laying the ball in. Calderon then knocked down the subsequent free throw to put Toronto up 114-112.

"We knew they wouldn't leave [star forward] Chris [Bosh]," Raptors coach Sam Mitchell said. "So I changed the play I drew up, and Jose was able to turn the corner."

The Celtics had one more possession, but Allen's attempted put-back from close range missed at the buzzer.

Even with the loss, which snapped a three-game winning streak, the Celtics sport the league's top record at 33-7.

The Raptors, who won for the sixth time in eight games, improved to 23-19 as they defeated Boston for the first time in four tries this season.

"It was really important to beat them — so we could see if we could," Calderon said. "We knew how to play them after already playing them three times."

Raps shoot the lights out

Bosh and Anthony Parker scored 23 points apiece, while Andrea Bargnani added 20 points to go with seven rebounds and seven assists for the Raptors, whose 114 points were the most given up this season by the Celtics.

Precision shooting fuelled Toronto's torching of the NBA's stingiest team, which came in having surrendered a paltry 87.4 points per game.

The Raptors drained 58 per cent of their shots from the floor, including a sizzling 15 of 21 (71.4 per cent) from beyond the arc.

"Half the guys in our league couldn't shoot 15-for-21 if they were in a gym by themselves," said an incredulous Boston coach Doc Rivers. "It was almost like we didn't believe they would shoot another one."

Carlos Delfino was the Raptors' top long-range marksman, going 5-for-5 from the three-point range to account for all of his 15 points on the night. Calderon was 3-for-4 from three-point land, while Parker was 4-for-6 and Bargnani 3-for-6.

Toronto was also money from the line, nailing all 19 of its free-throw attempts.

Kevin Garnett topped all scorers with 26 points. He also notched seven rebounds and five assists for the Celtics, who shot 49.4 per cent from the floor.

Pierce and Allen — the other two-thirds of Boston's Big Three — had 19 points each, while Tony Allen chipped in 15 and Rajon Rondo contributed 14.