TEMPE — Jahii Carson’s first foul came 20 seconds into Arizona State’s rivalry game Saturday afternoon. His third — a charge, drawn by Kevin Parrom, after Carson weaved through half the Arizona Wildcats— was whistled with 10 seconds remaining in the same half.

His fourth foul, though, truly changed the game,

The Sun Devils trailed by two, 46-44, with 9:50 to play when Carson hacked the Arizona Wildcats’ Mark Lyons while he was shooting.

The UA’s 25-10 run the rest of the way — in an eventual 71-54 win — was an endless barrage of easy shots.

Carson was taken out of the game after his fourth foul, but returned less than two minutes later. The Sun Devils needed his offense, but essentially played 4-on-5 while on defense.

Consider how the Wildcats scored their 18 points when Carson was in the game but playing with four fouls: a Nick Johnson layup, Lyons layup, Kevin Parrom layup, Lyons layup, two Parrom free throws, another two Lyons layups, two Lyons free throws and two Parrom free throws.

“They did a good job of attacking him with four fouls,” ASU coach Herb Sendek said, “And he was understandably cautious.

“I thought, defensively, that was difficult for us.”

Johnson finished with 19 points on 7-of-13 shooting. Lyons went 8-for-15 for 24 points.

“We definitely wanted to get to the rim,” Johnson said. “With Jahii in foul trouble, I tried to attack him every time he was on me, try to get him either fouled out or not playing defense.”

Added together, the UA’s three leading scorers — Solomon Hill, Johnson and Lyons — were wildly efficient, making 21-of-39 shots.

“I thought their ability to drive the ball past our first line of defense, an then our second line, and finally over our bigs, our third line, was really effective,” Sendek said. “We had a difficult time from, really, the first offensive possession.”

The explosive Carson scored 22 on 7-of-13 shooting but couldn’t contribute defensively in the final 10 minutes.

He played 33 minutes anyway, in part because reserve Chris Colvin was forced to sit after violating team rules.

“He’s the heart of the team,” Hill said of Carson. “You can’t be careless in the situation like he is.

“They only have six or seven guys, and it’s a big drop off when Jahii’s out of the game.”

Carson trying not to foul with four fouls was “just being smart,” Hill said, and better than the alternative.

“You don’t want to see him off the floor if you’re an ASU fan,” Hill said.

Carson seemed frustrated by the calls.

He had looked forward to Saturday’s matchup — both with the Wildcats and his old friend Johnson, with whom he grew up. The two hadn’t faced each other since eight grade; earlier this week Carson Tweeted a photo of the two as boys.

“He’s a friend of mine, but when it comes game-time, I really wasn’t worried about him,” Carson said , “I wasn’t worried about what he was doing. I was worried about winning the basketball game.

“It’s cool that we were kids growing up (together), but when we step on the floor it’s game-time.

“I want to cut his head off; I’m pretty sure he wants to cut off mine.”

Carson smiled.

“I was happy for him, of course, always,” he said. “But I’m more disappointed we didn’t get the win and go out and compete the way I thought we should have.”

Carson and Johnson talked to each other throughout the game, both Phoenix-area natives.

Johnson sounded relieved after the win, both because of the opponent and location. The last time he played at Wells Fargo Arena, Johnson scored only five points and was played limited minutes after picking up four fouls.

The UA lost to ASU last March, effectively sinking its NCAA tournament hopes.

“You always want to play good in front of your hometown,” the UA sophomore guard said. “That’s definitely a big thing. I already had enough motivation to get better, to keep on working.”

He told Carson, after the game, to keep working, too.

“We’re both from the same area, and I wanted to see him do good,” Johnson said. “Just maybe not against us.”