The Boston Celtics handed LeBron James and the Los Angeles Lakers their worst defeat of the NBA season on Monday, routing the Western Conference leaders 107-139.

Jayson Tatum scored 27 points and Kemba Walker returned from injury to add 20 for the Celtics, who snapped a three-game losing streak with the upset triumph.

Enes Kanter came off the bench to score 18 points and pull down 11 rebounds for the Celtics, who had lost six of their past eight games.

“Listen, it was just a good, old-fashioned butt-whipping, that’s all,” said James, who scored 15 points and handed out 18 assists for the Lakers – who had won 10 of their last 11.

“They beat us in all facets of the game,” added James, who said 15 Lakers turnovers leading to 28 Celtics points and Boston’s 48-36 rebounding advantage were too much to overcome.

The Celtics spoiled the return from injury of Anthony Davis, who missed five games with a bruised backside suffered during an in-game fall.

For Walker, it was a first career win against James. He’d gone 0-28 in prior games against James-led teams.

Simmons fuels 76ers

Philadelphia’s star guard Ben Simmons matched his career high with 34 points and added 12 rebounds and 12 assists in a triple-double that propelled the 76ers to a 117-111 victory over the Nets in Brooklyn.

Simmons, named during the game as the NBA’s Eastern Conference player of the week, did it all in a dominant performance for a 76ers team trying to keep their playoff push on track despite the absence of injured big man Joel Embiid.

The Aussie star connected on 12 of 14 from the field in his fifth straight game with 20 or more points, achieving his fourth triple-double – posting double figures in three key statistical categories – of the season.

For good measure, he added five steals and two blocked shots. “Ben was ridiculously dominant tonight,” 76ers coach Brett Brown said. “He was just multi-skilled, used all over the place in multiple positions, ball-handler, screen setter, post target. He was incredible.”

Spencer Dinwiddie scored 22 points for the Nets, who led by 10 in the third quarter but dropped their fourth straight.

Philadelphia, holding down sixth place in the Eastern Conference, notched their fourth straight win.

Eastern Conference leaders Milwaukee improved their league-leading record to 39-6 with a 111-98 victory over the Chicago Bulls.

Reigning NBA Most Valuable Player Giannis Antetokounmpo posted a triple-double of 28 points, 14 rebounds and 10 assists as the Bucks notched a seventh straight win.

The Bucks were slowed by 23 turnovers – 15 in the first half – but held on to beat the Bulls for a 10th straight time.

Khris Middleton added 24 points for the Bucks, who were headed Monday night to Paris where they take on the Charlotte Hornets on Friday in the first NBA regular-season game in the French capital.

“Obviously, a game like this is kind of a tricky game,” Antetokounmpo said, adding that preparations for the trip to France were a bit distracting. “I think we did a better job coming out in the second half, playing with some energy, being more aggressive and being more sharp.”

The Miami Heat needed overtime to stay in second place in the East, rallying from an eight-point fourth-quarter deficit to triumph 118-113.

The Heat, trailing the Bucks by eight games, remained a game in front of the reigning champion Toronto Raptors, who pushed their winning streak to four games with a 122-117 victory over the Hawks in Atlanta.

Houston’s Russell Westbrook notched another iconic triple-double moment, but his 32-point, 11-rebound, 12-assist performance for the Rockets wasn’t enough in a 112-107 loss to the Oklahoma City Thunder.

Westbrook played his first 11 seasons for Oklahoma City, and they were the only team he hadn’t recorded a triple-double against. He joined James as the only players in NBA history to notch a triple-double against every team in the league.

But the Thunder, aided by 28 points from Chris Paul and 25 from Danilo Gallinari, erased a 16-point fourth-quarter deficit to grab the win.