Nets guard Caris LeVert blocks the shot of Celtics guard...

Nets guard Caris LeVert blocks the shot of Celtics guard Carsen Edwards during the first half of an NBA game on Wednesday in Lake Buena Vista, Fla. Credit: AP/Ashley Landis

One night after shocking the NBA by upsetting the league-best Bucks as 19-point underdogs, the Nets were shockingly bad against the Celtics despite needing just one win to clinch a playoff berth. The Nets suffered a 149-115 blowout loss Monday night at Disney World in Orlando.

Starters Joe Harris (14 points), Caris LeVert (13) and Jarrett Allen (11 and eight rebounds), all of whom sat out against the Bucks, returned but left the game midway through the third period because it was out of hand. The Nets (32-36) actually were led by 20 points from Jeremiah Martin off the bench.

The Celtics (45-23) got 21 points from Jaylen Brown, 19 from Jayson Tatum and 18 from Gordon Hayward and Robert Williams III, and they were 20-for-39 from three-point range (51.3 percent).

The Nets are 2-2 since the restart and still tied for seventh place in the Eastern Conference. With one win or a loss by the ninth-place Wizards, who are 0-4 in the restart, they can clinch a playoff berth. Interim head coach Jacque Vaughn is 4-2 since replacing fired coach Kenny Atkinson despite a roster decimated by injury and illness.

“We talked about it as an organization that the standard, the goals wouldn’t change just because some of our roster changed coming to Orlando,” Vaughn said before the game. “We were coming to compete and win every basketball game. That hasn’t changed. It’s been great to see our guys accept that standard and perform.”

The Celtics, who rested point guard Kemba Walker, and it seemed the Nets carried some momentum over from the Bucks win as they took an early 24-23 edge.

But things fell apart during a 20-1 Celtics run, including nine points from Hayward and seven from Robert Williams, that spanned the first and second quarters to build a 43-25 lead. The Nets missed all eight field goal attempts and committed three turnovers during that stretch. The Celtics led by as many as 21 points in the second quarter on their way to a 71-52 halftime lead.

“We kind of got away from what led to a lot of our successes these last two games,” Harris said. “We didn’t rebound the ball well, we didn’t defend well, a lot of turnovers, not a lot of assists. We weren’t making that extra pass that we have been, and there were a lot of 50-50 balls that we didn’t get either. We just got outworked against a team that is obviously just more talented, and when you do that, you’re going to lose the way we did.

It got much worse in the third period when Brown scored 14 points in an extended 28-16 run for a 99-70 lead, and a Tatum three-pointer pushed the Celtics’ lead to a high of 31 points at 106-75 when the period ended.

Vaughn admitted the Nets’ three-point defense not only broke down, but they foolishly fouled three-point shooters three times.

“We definitely had some breakdowns tonight,” Vaughn said. “Definitely, challenge the group to be better on Friday [against the Kings], which I think they will respond. It’s an opportunity for us to see how we can regroup.”

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