For the first time in two years — a span of 40 games — Stanford has a Pac-12 blemish. And just like that, the conference is locked in a three-way tie for first place.

USC on Sunday became the first conference foe to topple the Cardinal since UCLA on Jan. 22, 2021. The stunner was the culmination of another tumultuous weekend.

The only teams to win twice were USC and Washington State, both of which were unranked.

Three ranked teams (No. 2 Stanford, No. 8 UCLA and No. 21 Oregon) all lost one of their two games.

And 14th-ranked Arizona lost twice on the road, against Colorado and No. 10 Utah. Clearly, the Mountain schools benefited — and the Wildcats suffered — from Arizona State having to forfeit its games against the teams because of a lack of healthy players.

As a result, Stanford, Utah and Colorado are tied for first at 5-1 in conference play, with UCLA one game behind and six weeks remaining in the regular season.

And guess what? The Mountain schools visit Stanford this week.

Eight teams have at least 13 overall wins, and everyone but ASU (7-9) has reached the double-digit victory mark.

Colorado is pushing to join the AP top-25 poll, while Oregon’s AP slot is looking tentative.

“The conference is fantastic,” Stanford coach Tara VanDerveer said. “I think it’s the No. 1 conference in the country.”

That evaluation came before the loss to USC 55-46 — the Trojans’ first win over a team ranked as high as Stanford since 2008, when they also toppled the Cardinal.

USC defense brings down Stanford

The Trojans (13-4) won without their leading scorer, Kadi Sissoko, with their second-leading scorer (and top rebounder) Rayah Marshall in foul trouble, with a seven-player rotation and with paltry 27.3 percent shooting from the field.

It was a testament to their defense — and to Stanford’s recent shooting woes, particularly from 3-point range — finally catching up to the Cardinal.

Stanford (17-2) took a two-point lead into the fourth quarter Friday at UCLA, then pulled away down the stretch thanks to the Brink truck.

Pac-12 Player of the Week Cameron Brink had six blocks, seven rebounds and six points during a dominant fourth quarter as the Cardinal secured a 72-59 win that seemed like it would be the toughest test of the weekend.

Instead, Stanford fell behind by nine points at USC and never led; it shot 19 percent from 3-point range (4-of-21) and 30.9 percent overall. Only Brink had decent numbers (11 points and 14 rebounds).

“I don’t know that we can do anything any worse,” VanDerveer said. “This has to be rock bottom in terms of execution offensively, lack of screening.”

“We were connected on all levels,” said Destiny Littleton, USC’s transfer from that other USC (top-ranked South Carolina). “I was guarding (Brink). I just stepped up and did what I needed to do. At the end of the day, we came together as a whole, and our defense is what won the game.”

A 7-0 surge put the Trojans up by 10 points going into the fourth quarter. From 8:04 in the fourth until there were 28 seconds left, Stanford made just one field goal.

The point total was Stanford’s lowest since January 2016, when it scored 36 against UCLA. The Cardinal’s only previous loss this season was to South Carolina, 76-71 (in overtime) in November. Its 51-game winning streak against unranked opponents ended.

“I just thought we really took care of business this weekend, which is the understatement of the century,” said USC coach Lindsay Gottlieb, whose team beat Cal by 20 points on Friday.

Arizona, Oregon, wins snatched away

While nothing can eclipse Stanford’s loss as the top story in the Pac-12, two other games on Sunday featured one-point finishes that the losing teams appeared to have won.

Arizona freshman Paris Clark scored twice in the final eight seconds – first off her rebound, then off a steal – for a 79-78 Wildcat lead at Utah with 1.6 seconds remaining.

But Gina Kneepkens heaved a long inbounds pass to Alissa Pili, who was fouled with 0.3 seconds remaining and made both free throws for a Utes win.

Pili scored 27 points with Kneepkens added 20 in a riveting game that had 17 lead changes and 14 ties.

“I just love that we didn’t panic,” Utes coach Lynne Roberts said. “We work on end-of-game situations all the time. We’ve run that before in practice. Alissa just made a heck of a play … just a great, great college basketball game.”

In Eugene, Oregon appeared to escape a five-point hole against Washington State with eight seconds left thanks to a 3-pointer by Endyia Rogers, then another by Ahlise Hurst, but Hurst’s basket was negated by a clock issue.

The Ducks still forced overtime on a pair of Grace VanSlooten free throws and had the last shot in the extra period — a difficult runner by Te-Hina Paopao that didn’t find the bottom of the net in an 85-84 loss to the Cougars.

“As poorly as we played at times, we had a chance to win the game,” Oregon coach Kelly Graves said. “That’s all you can ask for. It’s disappointing, but we just didn’t have enough players have good games.”

“We kind of showed the rest of America we are good,” said WSU junior Jessica Clarke, who scored four of her career-high 14 points in overtime.

It was Washington State’s first road win over a ranked Pac-12 opponent since 1998.

“I can’t even express how happy and excited I am for this team,” Cougars coach Kami Ethridge said. “I told the team before the game that it feels different with our team, with how they respond to adversity this season.”

Impact of ASU forfeits

ASU’s forfeits clearly were an advantage for Colorado and Utah, which played only one game for the second consecutive week following their rivalry meeting on Jan. 6.

Under first-year coach Natasha Adair, the Sun Devils have been shorthanded since November, with three players – Maggie Besselink, Morasha Wiggins and Jaylah Robinson – out for the year.

They had nine players available against Oregon State on Jan. 8 and, apparently, even fewer last week when the decision was made to forfeit two games.

“The reality is there was no decision to be made,” Adair said in a statement. “With few healthy scholarship players, time to heal is our only option. Our plan is to get our team healthy over the course of this week and be ready when we host Arizona (on Sunday).”

VanDerveer, the Pac-12 career wins leader,  was only somewhat sympathetic when asked Friday about ASU forfeiting.

“It’s a responsibility of the coaches to have a full roster,” she said. “It’s challenging when you have a new coach, the portal and people leave.

“Part of it is keeping people healthy. That’s a big part of the job. You have to weather that storm.”

ASU also forfeited a game at Cal last season because of travel complications.

Per NCAA rules, ASU’s losses and the wins for Utah and Colorado are counted only in Pac-12 standings and not in the overall record.

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