OAKLAND, Calif. — Kenny Atkinson wanted to see how his team responded to arguably the toughest challenge in basketball — facing the Warriors in Oakland on the second night of a back-to-back.

They couldn’t back up their victory in Denver with another against the defending champions. They couldn’t come close, beaten 116-100 by shorthanded Golden State before a sellout crowd of 19,596 at ORACLE Arena.

“We ran out of gas, ran out of energy,” Atkinson said. “I thought our second group, the ball started sticking. I thought we played too much iso ball. You can’t do it against this team. You can’t just line up and play one-on-one basketball. One thing I am disappointed in is that we weren’t playing Nets basketball.

“Fatigue played a big part of it and mental sharpness. All-around, the team was not sharp, the defensive coverages, our offense, we were not where we needed to be to compete with this team.”

The Nets (6-7) came in riding a three-game winning streak and having taken four of their past five for the first time since 2016-17. And they’d battled Golden State to within a basket with a minute left before falling 120-114 on Oct. 28.

But Saturday’s rematch was nowhere near that close, despite the Warriors (11-2) playing sans Steph Curry, Draymond Green and DeMarcus Cousins (Achilles). Kevin Durant (game-high 28 points, 11 assists) and Klay Thompson (24 points) abused the Nets accordingly. But allowing 25 to unheralded Quinn Cook should stick in their collective craw.

“Coach said it best: We’ve got to prepare mentally better in those situations, those back-to-back games like that,” said Caris LeVert, who suffered through a tough night.

The rising young guard had been averaging 20.3 points. But after hitting the game-winner Friday in Denver, LeVert mustered just four points on 1-of-6 shooting with no assists. He, like the rest of the Nets, got lured into playing too much isolation by the Warriors’ switching defense.

“They’re one of the best switching teams in the league,” LeVert said. “They force you to think you have to take a lot of iso situations. The first couple minutes of the game, we were doing a better job of sharing it. We’ve just got to figure out how to do that for the full 48 minutes.”

Joe Harris had a team-high 24 points on 9-of-12 shooting, but D’Angelo Russell was the only other starter in double figures with 12. Spencer Dinwiddie and Shabazz Napier each had 14 off the bench.

“We had a difficult time getting the ball second side, trying to get them moving,” Harris said. “We had a tendency to just get into isolation situations, and from there, our offense stalled.”

Fell apart is more apt. They led by six in the first quarter and were still within 59-53 after Russell hit Rondae Hollis-Jefferson for a driving layup with 3:18 left in the half. But that’s when the ball movement — and the offense — disappeared. They allowed a 13-2 run that spanned halftime and doomed them.

“We missed a lot of shots,” Russell said. “We had a few breakdowns as well on the defensive end, but we missed a lot of shots. They came down and capitalized with 3s or and-1s or wide-open layups. It’s hard to bounce back off that.”

The Nets went 1-for-12 in their drought, 0-for-6 from deep, and committed three turnovers. LeVert and Russell combined to go 0-for-10 from the floor and 0-for-5 from behind the arc.

By the time Damian Jones dunked and converted an and-1, Brooklyn trailed 72-55 and the game was over. The Nets trailed by as much as 24.

They wrap up the four-game road swing Monday in Minnesota.

“I want to see how we bounce back from this. A 20-point loss is a 20-point loss,” Atkinson said. “It’s an important game to test our character.”