SAN ANTONIO — The Nets were already missing both Kevin Durant and Kyrie Irving on Tuesday night, but it was an ill-timed foul by Ben Simmons that did them in as they lost 106-98 to a sad Spurs team before a crowd of 13,532 at AT&T Center.

And it was a third-quarter dry spell with Simmons on the bench that proved too much to handle.

Keldon Johnson poured in a career-high 36 points to light up the Nets (27-16). But with Durant out with a sprained right MCL and Irving a late scratch with a sore right calf, the Nets predictably suffered on offense, even against the woebegone Spurs (14-31).

The Nets mustered just 15 points in the first quarter, went 3-for-23 overall from 3-point range and yet were still in the game midway through the third quarter. That is, until Simmons — who had a triple double with 10 points, 10 rebounds and 11 assists — picked up his fourth foul and went to the bench with 7:47 left in the third.

With the score knotted at 58-58, the Spurs promptly went on a 6-0 run. The Nets never recovered.

“Well, you know we need everybody and that’s a big piece of it,” coach Jacque Vaughn said. “So we have to be disciplined and smart how we play the game. And a big piece of that is — I talked about that before the game — the rebounding and the fouling. We have to take care of it.

“And it is in multiple fashions. Whether it’s the rebounding piece, whether it’s reaching on the guy who drives, whether it is being not positioned and then having to react. So all culprits of it. And hopefully guys are starting to understand the discipline along the way, it has to be there, because you won’t be able to recover from stretches like that. And so, great challenge for a group.”

Apparently a stint with none of their Big Three on the court was too big a challenge.

Simmons didn’t return for the rest of the third quarter as the Spurs’ run reached 18-10. The Nets trailed 76-68 entering the fourth quarter, and they never got closer than four points the rest of the night.

“Obviously it’s frustrating to pick up your fourth. I think it’s a game of runs. … I don’t think we managed it well. We needed to get stops and that’s where we flourish, getting stops, getting out in transition. Too many fouls, too many turnovers, no transition which is really what the game was,” said Simmons, who was champing at the bit to get back in, four fouls or no.

“As a competitor, I want to stay in the game regardless if I got four because I got two more to give. So I kind of want that trust in coach for him to just leave me out there. I’ve been in situations where I’ve had four fouls, and you’ve got to trust your guys. So … yeah.”

Vaughn cautiously left Simmons planted next to him on the bench next for the rest of the third quarter. The Nets never regained any momentum.

The Nets got as close as four twice: at 82-78 when Seth Curry, who had 16 points starting in place of Irving, hit a 3-pointer on a kick out from Nic Claxton, and again on a Simmons drive to make it 84-80 with 7:48 to play.

T.J. Warren led the Nets with 19 points, while Claxton fouled out with 15 points, 11 rebounds and four blocks.

“It was a big foul. Ben sometimes got to learn with fouls without fouls I think that was one of those situations where it’s like up in the air. But that affected us and it kind of effected our momentum a little bit,” said Markieff Morris, who had to be separated from Jeremy Sochan in the second quarter after he put a hard screen on the Spur and got taken down by the rookie. “He actually did a wrestling move to me. I said that was impressive. I told him that.”

Asked what he knew about Sochan coming into Tuesday, Morris said: “He was a draft pick this year, he’s got yellow hair, shooting one handed at the free throw line.”

Now? “He’s still got yellow hair.”