Aari McDonald burst past a sea of Sun Devils, laid the ball in, stole the ensuing inbounds pass, and promptly knocked down a mid-range jumper before flexing and shouting.

“She’s our catalyst on offense and defense,” said Arizona coach Adia Barnes.

McDonald, the nation’s third-leading scorer, dropped 24 points and Arizona used a stellar defensive effort to upset the No. 17 Arizona State Sun Devils 51-39 on Sunday in Tucson in front of 5,006 raucous fans to open Pac-12 play.

It’s the first time Arizona (11-1) has won its conference opener since 2012-13, and the first time it has beaten a ranked team since the 2015-16 season, the strongest proof yet that Barnes is lifting the UA program out of a decade-long abyss.

“Arizona State is a great team, they are ranked and this will definitely prove that we can do some big things in this conference,” said McDonald, who sat out last season due to NCAA transfer rules.

Winners of 10 straight, the Wildcats held a usually-potent ASU team to 23 percent shooting, their defensive intensity never wavering. Arizona forced 17 turnovers and grabbed seven more defensive rebounds than the Sun Devils, who boasted a +14.4 rebounding margin entering the night.

“I’m proud of the way we won every passion play, we won every 50-50 ball, we had some awesome defensive stops and our defense was spectacular,” Barnes said. “That’s all their work.”

Arizona had not played a major-conference team entering Sunday’s game, leading some to question whether or not they were truly prepared to battle a Top-20 squad like ASU.

Those concerns were quelled in a hurry. The Wildcats, who led wire-to-wire, jumped out to a 9-2 lead in the early goings, thanks to seven quick points from McDonald.

“That was huge,” she said. “For us to come out strong like that, that definitely gave us confidence and gave us momentum for the rest of the half.”

McDonald went 9 for 17 from the field and 6 of 7 from the charity stripe, leaving Sun Devil defenders in the dust all night.

“I don’t know anyone in the country that can guard her off the dribble,” Barnes said.

Or pester ball-handlers the way she does.

“Her on-ball defense is amazing,” UA forward Sam Thomas said of McDonald, who had six rebounds and three steals. “She’s one of the best I’ve ever seen. So it really helps when she’s denying the ball handlers and they get flustered and then we have to deny our man and then it just really helps break down their offense and get us those defensive tips.”

ASU clawed back to tie the game at 11 then 13, but McDonald scored, stole the inbounds pass and scored again to push UA’s lead to 17-13 at the end of the first.

Tee Tee Starks made a similar play late in the second quarter, spinning in a reverse layup then draining a 10-footer to extend the lead to nine with 31 seconds left in the first half.

ASU’s Kiara Russell knocked down two free throws to cut ASU’s deficit to 27-20 heading into the locker room.

“It definitely feel great to get four points like that,” McDonald said of Starks’ effort, “and we definitely went into halftime with the momentum.”

3-point shooting was at a premium, with both teams going a combined 5 for 31, but Thomas made UA’s first triple with 5:34 left in the third that put Arizona up 30-23, halting what wound up being ASU’s best opportunity for a comeback.

Thomas, who finished with 11 points, scored again to make it 34-25, then Destiny Graham notched her first points to extend the lead to 11 with 3:28 left in the third.

ASU whittled its deficit to seven three different times in the fourth, but never closer than that. Arizona always had an answer — and then some.

McDonald zoomed for an uncontested layup to put Arizona up nine with 3:08 left. Dominique McBryde, who poured in six points and nine rebounds, drained a mid-range jumper to put Arizona up 11 in the final two minutes, then Thomas converted a breakaway layup on an outlet pass from McDonald to make it a 15-point game with 71 seconds left.

Thomas, a sophomore who was part of last year’s team that went 6-24 and lost thrice to ASU, was all smiles after the game. She knew what this win meant for the upstart UA program.

“I’m just so happy right now,” she said. “It’s just great to know that we got that first Pac-12 win coming off the break and non-conference. It was just great to secure this one against our rivals, and know that now in the new year we can just keep getting better and better.”

For the first time in Barnes’ tenure, the present is as bright as the future.

“We have confidence, we’re on a 10-game winning streak, we’re playing some good basketball, so this is exactly where I wanted to be,” said the third-year coach, who took over a floundering program in 2016-17. “Tonight showed me where we’re at ... because we played a really good defensive team and we played really good defense, so it shows me that we’re going to be one of the best defensive teams in the conference.

“Does that mean we’re going to win the Pac-12? Not necessarily, but it means that we can surprise some people and that’s what we’re gonna do.”

Postgame videos

Adia Barnes

Sam Thomas and Aari McDonald