Once Carson picked up his fourth foul, the Wildcats ran away from their biggest rival.
Mark Lyons scored 24 points, Nick Johnson added 19 and No. 7 Arizona pulled away in the second half after Carson picked up his fourth foul to beat the Sun Devils 71-54 on Saturday.
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"He's the heart of the team," said Arizona forward Solomon Hill, who had 13 points, six rebounds and five assists. "They've only got six or seven guys and it's a big drop off when Jahii's out of the game."
It was more than just getting Carson in foul trouble, of course
Arizona (16-1, 4-1 Pac-12) was solid at both ends, hitting 14 of 25 shots in the second half and stymieing the Sun Devils at the defensive end all game.
The Wildcats forced Arizona State into 17 turnovers - leading to 18 points - and freshman Brandon Ashley had the best defensive game of his young career, helping to hold Carrick Felix, Arizona State's second-leading scorer, to five points on 1-of-8 shooting.
Arizona also managed to get Carson in foul trouble, picking up a charging call against him just before halftime and another foul on a hard drive by Lyons midway through the second. The Wildcats capitalized with Carson out, using a 9-0 run to build an 11-point lead that was never really challenged.
"That was a hard-fought road win," Arizona coach Sean Miller said. "One of the reasons we ended up winning like we did is our defense really returned to us tonight. I'm sure they had some shots that they look at they've got to make, but for the most part our defense fueled us."
Arizona State (14-4, 3-2) never recovered after Arizona's run.
Playing without guard Chris Colvin, who was benched for violating team rules, the Sun Devils struggled with Felix settling for 3-pointers instead of being aggressive - 1 for 7 from beyond the arc - and Carson out with his fourth foul. Arizona State also was hurt by turnovers, which led to easy points for the Wildcats at the other end, and had a hard time stopping Arizona's guards from getting to the rim, particularly Lyons in the second half.
Carson had 22 points, four rebounds and four assists, but had to play tentatively the final 10 minutes of the game because of his fouls.
"They did a good job of attacking him with four fouls and he was understandably cautious," Arizona State coach Herb Sendek said. "I thought defensively, that was difficult on us."
The basketball version of the Territorial Cup featured one of the most anticipated matchups in the rivalry's recent history.
Arizona opened the season loaded with hype and has lived up to it, climbing to No. 3 in the AP Top 25 after winning its first 14 games. The Wildcats have one of the Pac-12's best backcourts in Lyons and Johnson, and a good mix of veterans and talented newcomers in the front court.
Arizona State has had a bit of a resurgence under Sendek behind a faster tempo and aggressive man-to-man defense. Carson, the flash-bulb-quick point guard, has been a big part of it, but Felix has emerged as one of the conference's best two-way players and the Big Bachynski, 7-foot center Jordan, has anchored the center of a defense that blocks one out of every eight shots taken by opponents.
The Sun Devils have gotten the better of their rivals recently, too, winning seven of the previous 11 in the series, including an 87-80 win in last season's finale that all but knocked the Wildcats out of the NCAA tournament.
With the highest-ranked opponent to play at ASU's Wells Fargo Arena in five years, not to mention that it was the hated Wildcats, the quaint arena got a jolt of energy, with the Sun Devils' students trading chants with fans of the team from down south.
After an initial surge that lived up to the game's hype, Arizona State went into an offensive funk in the first half, hitting two shots after the 11:12 mark before Evan Gordon picked Lyons' pocket for a steal and a layup just before the buzzer to cut Arizona's lead to three.
Arizona opened the second half with a small spurt to go up nine points, but the Sun Devils fought back, pulling within 46-44 on a layup by Carson after a nice bounce pass from Gordon on a backdoor cut.
But on Arizona State's next possession, Felix dropped a pass from Carson that would likely have resulted in a layup. Carson then picked up his fourth foul on Lyons' drive at the other end and headed to the bench with 9:50 left.
Arizona followed with its decisive run, going up 55-44 on a layup by Johnson that forced Sendek to call a timeout.
Sendek gambled by bringing Carson back in a few minutes later, but the damage had been done and the Sun Devils never climbed back out of the hole.
"I don't think we played to the best of our capabilities," Carson said. "Normally, we come out and set the tempo, we throw the first punch, and I think they did that. I think they wanted it more than us."