MIAMI — As poorly as the Nets had played recently and as far as they had fallen, they absolutely had to win Saturday night.

So they beat down the Heat and won.

Mired in their worst losing streak of the season, the Nets came through with their biggest gut-check, turning a second-half blitz into a 129-100 rout of the Heat before a sellout crowd of 19,680 at Miami-Dade Arena that — for the moment — moved them out of the precarious play-in tournament.

The Nets trailed by as many as 14 points in the first half and were still down by 12 with just over two minutes left before the break.

But they used an extended 44-11 run that spanned intermission to break the Heat — and their five-game skid.

The victory vaulted the Nets (40-34) a half-game ahead of Miami and back into the sixth and final guaranteed playoff spot in the Eastern Conference.

“Coming in, I thought it was a must win. I think that the whole locker room did,” Cam Johnson said. “But this is as close to a playoff game with big implications that we’ll get at this time of the year, and as close to you get in the regular season. So this was a big one for us, and just one that we kind of beared down and got it done.”

After they defeated Miami on Jan. 8, the Nets had won 18 of 20 games and were just a half game behind the Celtics for the best record in the NBA.

But Kevin Durant sprained his right MCL that day in South Florida, and the butterfly effect is still being felt throughout the entire league.

Durant never played for the Nets again, and he and Kyrie Irving forcing the team to trade them.

And on Saturday, the two players that came back from Phoenix in the Durant deal helped the Nets to a slump-busting laugher.

“Yeah, we were pretty calm and collected at halftime,” head coach Jacque Vaughn said. “We took a punch from them on the road. We didn’t flinch, which was good.”

Mikal Bridges poured in a game-high 27 points and seven assists, while Johnson added 23 points on 5-for-8 shooting from deep.

“We just stayed together. That’s the biggest thing staying together as a team,” Bridges said. “We did a great job of coming out and staying focused. We need every game, especially this one. We just came out and fought and played really hard.

“It shows when times get tough, we stay together. We could easily be upset about the last couple of losses; we lost like five in a row. But we just came out and competed and played hard the whole 48. … It was just great. We stuck together. Times got tough and we stuck as a team.”

The Nets stuck together against the Heat (40-35), although they were a sieve to start, allowing 13-for-16 shooting in the first quarter and 6-for-7 from 3-point range.

The Nets trailed 51-37 after a layup by Max Strus, who hit his first nine shots and finished with 23 points.

It was 64-52 after a Bam Adebayo dunk with 2:35 left in the first half, but that’s when the Nets took over.

They closed the second quarter on a 13-5 run, and they carried that momentum into a 31-6 start to the third quarter.

They credited Nic Claxton’s defense and Ed Sumner’s energy for turning the tide.

After they had been unable to stop the Heat early, suddenly they held Miami to 4-for-18 shooting, including 1-for-7 from behind the arc.

Thayt strong defense allowed the Nets to finally get out and run. They got clean looks in transition and early offense.

They went 17-for-23 from the floor, and 9-for-13 from deep.

A floater by Spencer Dinwiddie (15 points, nine assists, seven rebounds) made it 96-75 with 3:58 left in the third.

Sumner darted the length of the court on a four-second fast break, hurling his body in for a layup at the buzzer to make it 104-87 after three.

The lead swelled to 32 in the fourth.

“We know how much these games mean. That last loss as bad on our part and we have no excuse for that,” Sumner said. “We have to stay together and keep our minds sharp and be ready to compete every night.”