The Raptors went on a 19-0 fourth-quarter run as the Celtics went more than six minutes without scoring.
Al Jefferson had 20 points and 10 rebounds for the Celtics, who have lost 10 straight -- their longest skid since losing 10 in a row from March 20 to April 7 in 2000.
The Celtics are missing Paul Pierce, Wally Szczerbiak and Tony Allen.
Hornets 88, Kings 84
At New Orleans, Desmond Mason scored 24 points and Bobby Jackson added 15 against his former team to help New Orleans hold off Sacramento.
Devin Brown, filling in for injured guard Chris Paul, scored 14 for New Orleans. He hit a three-pointer as the shot clock ticked down and a clutch free throw, both in the final 30 seconds, to thwart a Mike Bibby-led charge by the Kings.
Bibby and Kevin Martin each scored 21 points for the Kings, who tied it at 82 with about 1:30 to go.
Tyson Chandler had 13 points and 12 rebounds for New Orleans, and his basket inside gave the Hornets the lead for good at 84-82.
John Salmons scored 14 points and Ron Artest grabbed 12 rebounds for Sacramento.