Horford, 38, led the Celtics scoring with 26 points off the bench.
Jayson Tatum added 25 points and 14 rebounds and the Celtics defense stymied the Grizzlies in the second half to complete a perfect 6-0 road trip – the longest unbeaten road swing in the club’s history.
Boston, second in the Eastern Conference behind the Cleveland Cavaliers, won all six games by double digits.
Horford scored his season-high, draining six of Boston’s 21 three-pointers.
“It’s a lot of fun,” Horford said. “It’s pretty amazing for me to be in this position and I’m just trying to have fun with it and enjoy with my team.”
Ja Morant scored 26 points for the Grizzlies, who led by as many as 11 in the first half and regained the lead early in the third.
Ultimately, however, they couldn’t keep pace and lost ground in their fight with the Los Angeles Lakers for fourth place in the West.
The Oklahoma City Thunder, already assured of the Western Conference top seed, racked up their 10th straight victory with a 145-117 pounding of the Chicago Bulls.
Meanwhile, Isaiah Joe came off the bench to score 31 points – leading seven Thunder players to score in double figures as Oklahoma City improved to 28-1 against Eastern Conference opponents – the NBA record for most wins by a team against an opposing conference.
“We all have the same goal in mind,” said Joe, who made eight of the Thunder’s 23 three-pointers. “We know what we want to do at the end of the day and we know how to get there. We’ve just got to keep stacking days, stacking games.”
Elsewhere, the Indiana Pacers rallied from 16 points down in the third quarter to beat the Sacramento Kings 111-109 and maintain their grip on fourth place in the East.
Tyrese Haliburton scored 18 points and handed out 11 assists, drilling a three-pointer with just over one minute remaining that gave Indiana the lead for good.
The Los Angeles Clippers, eighth in West but locked in a battle with Golden State and Minnesota for sixth place and direct entry to the playoffs, clawed out a gritty 96-87 victory over the Magic in Orlando.
Kawhi Leonard and Norman Powell scored 21 points each and Ivica Zubac added 18 points and 20 rebounds – including nine on the offensive end – to help the Clippers finally seize control in a game that featured 15 lead changes in the first three quarters.
Paolo Banchero scored 26 points and Franz Wagner added 21 for the Magic, who remained in eighth place in the East.
The top six teams in the each conference advance to the playoffs while teams ranked from seventh to 10th play a mini-tournament to determine the final two playoff slots.
The Miami Heat climbed to ninth – ahead of the Bulls – with a fifth straight victory, beating the Wizards 120-94 in Washington.
Bam Adebayo scored 28 points and grabbed 12 rebounds and Tyler Herro added 27 points for the Heat, whose current winning streak comes on the heels of a 10-game skid. (AFP)
