NEW YORK — The 76ers have a problem — a sustained competitiveness problem.

Right about now, Saturday’s thrilling victory over the league-best Golden State Warriors looks more and more like a mirage.

» READ MORE: 76ers delay Curry's 3-point record bid, beat Warriors 102-93

That’s because the Sixers have been subpar and have had competitiveness lapses while losing their next three games. Their latest setback was a 114-105 decision to a Brooklyn Nets squad that only had nine available players Thursday night at the Barclays Center.

Unfortunately for the Sixers, losing to undermanned squads is nothing new. They suffered a five-point home loss Wednesday to the Miami Heat squad with just nine available players. And Monday’s 35-point road drubbing came to a Memphis Grizzlies team without standout point guard Ja Morant and four players altogether.

Now, the Sixers were minus starters Joel Embiid (sore ribs) and Seth Curry (shoulder soreness) on Monday. Reserves Georges Niang (COVID-19 protocols) and Furkan Korkmaz (non-COVID illness) were out Wednesday. And against Brooklyn, starting point guard Tyrese Maxey (left quadriceps contusion) joined Niang and Korkmaz as sidelined players.

“We’ve got to get everybody back,” coach Doc Rivers said. “We played a game tonight without a point guard ... with one power forward. I thought we were so small. We are in general a small team. But to lose Georges, now Tobias is your only four. [Danny Green’s] now playing four for us. So that’s difficult. You lose Tyrese and Furk, you lose a lot of ballhandling on the floor.”

» READ MORE: Sixers, Doc Rivers are looking for preventative measures to combat COVID-19

But the Sixers’ absences should not have mattered in their last two games, facing squads that are shells of themselves.

On Wednesday, the Nets (21-8) had seven players — James Harden, LaMarcus Aldridge, DeAndre’ Bembry, Bruce Brown, Jevon Carter, James Johnson, and Paul Millsap — sidelined due to protocols. Meanwhile, Kyrie Irving is ineligible to play due to being unvaccinated and Joe Harris is sidelined after left-ankle surgery.

Brooklyn was so thin that it had to use a 10-day hardship exception to sign the former St. Joseph’s standout Langston Galloway just to have nine available players.

But on this night, the Sixers dug too deep a hole early on and couldn’t fully recover.

Embiid looked at the last two losses as missed opportunities.

“Miami was missing their best players,” he said. “Tonight Brooklyn, obviously, they had KD, but they’re missing a bunch of players. Like I said, it [stinks] losing. It’s frustrating.”

Doomed by a slow start

The Sixers trailed by 20 points at intermission and at times looked disinterested. They played better after halftime, pulling to within one point (92-91) on Matisse Thybulle’s breakaway layup with 8 minutes, 19 seconds remaining in the game.

They pulled within 96-95 on Curry’s jumper with 6:02 left. And then Embiid knotted the score twice. The second time made it a 103-103 game with 1:55 left.

But they were ultimately doomed by what turned out to be another Kevin Durant showcase. The 11-time All-Star responded by draining a three-pointer while being fouled by Tobias Harris. Durant hit the foul shot to give Brooklyn a 107-103 lead nine seconds later. Then he assisted on a Blake Griffin three-pointer that put the Nets up 110-103 with 1:13 to play. Then Durant clinched the game with a six-foot jumper to make it 114-105 with 35.2 seconds left.

The Brooklyn forward displayed all-around skills while finishing with 34 points, 11 rebounds, eight assists and a block.

The loss dropped the Sixers to 15-15, marking their worst record through 30 games since going 14-16 during the 2017-18 season. That team managed to turn things around, however, finishing the regular season with a 52-30 record.

Time will tell if the Sixers can play a complete game.

Durant’s dominance

Durant logged 38-plus minutes for the sixth straight game. The four-time scoring champion played 39:02 against the Sixers. He made 13 of 24 shots, but also did a solid job of getting teammates involved.

“Kevin, he’s just incredible,” Nets coach Steve Nash said. “His level of play is insane. Efficiency, leading the league in scoring [at 29.6 points per game before Thursday] with as few shots as it takes for him to do so is incredible in its own right. Some of the nights he’s had to close games down the stretch, to defend at the rate he’s defended at, you put it all together and it’s an incredible start to the season.”

Embiid paced the Sixers with a team-high 32 points to go with nine rebounds. Harris had one of his worst performances of the season, finishing with 11 points on 3-for-17 shooting.

Rivers disappointed with foul disparity

Rivers was bothered that the Nets were called for zero fouls in the fourth quarter. He even called a timeout with three seconds remaining to voice his displeasure with not getting a foul call. Rivers even held his hand in the shape of a zero.

“I thought Joel got fouled the last three post possessions, and-ones and nothing was called,” Rivers said. “I don’t know a team can play in the fourth quarter and in a game where we’re driving the ball and posting the ball and they have zero fouls.

“It’s hard to play a quarter in the NBA and commit no fouls. So very surprised by that.”

Next up

The Sixers will have two days off before hosting the New Orleans Pelicans on Sunday at the Wells Fargo Center. The Pelicans are the league’s fourth-worst team at 9-21.