SEATTLE - Somewhere in a week of meetings and assessment, honest accountability and motivational speeches, the same Washington State team that looked lost a week earlier found a needed spark.

The Cougars discovered it just in time to stun their rivals and keep their slim postseason hopes alive.

"There is not a better feeling in basketball than winning in your rivals' gym and seeing their fans file out early," Washington State's Klay Thompson said.

Thompson overcame a sloppy first half to score 26 points, DeAngelo Casto added 20 on the inside and Washington State completed the season sweep of Washington with an 80-69 victory Sunday night.

Thompson came up big against the Huskies for the second time after scoring 25 in an 87-80 win last month in Pullman that started Washington on a costly three-game skid.

Now it was the Cougars (18-10, 8-8 Pac-10) ending Washington's hopes - however slim - of a Pac-10 regular-season title.

It was equally impressive and stunning for the guys in crimson, who heard their pockets of fans chanting "Let's go, Cougars!" in the final minutes while those in purple quietly filed out. The same Washington State team that had stumbled at last-place Arizona State just eight days earlier became the first road team to win on Washington's home floor in more than a year, snapping the Huskies' 14-game home winning streak.

The Cougars made this one ugly from the start, frustrating the Huskies at the defensive end and holding Washington to 17 points in the first half, the fewest in coach Lorenzo Romar's tenure at his alma mater. Washington State led by as many as 21 in the second half, then held off a furious Washington charge in the closing minutes.

The Cougars were helped by hitting 32 of 36 free throws for the night, including 25 straight at one point. That performance at the free throw line came from a team shooting 69 percent for the season.

"We kind of slapped ourselves in the face when we lost to ASU," Casto said. "We pushed ourselves against a wall, and this is a team that is capable of a lot of things, but we've got to show up every game. ... We wanted to come out and show we weren't going to keel over at the end of the season."

On this night, every loose ball and every hustle play went the way of the Cougars. Casto added 13 rebounds and kept plenty of other plays alive. Casto and Brock Motum outplayed Washington post Matthew Bryan-Amaning, who went scoreless for the first 26 minutes before coming on late and finishing with 14 points.

Isaiah Thomas led the Huskies (19-9, 10-6) with 21 points but got little help otherwise. And now Washington is left with work to do just to secure its postseason fate. What seemed a lock not too long ago is now a bit more tenuous with home games against UCLA and USC remaining before the Pac-10 tournament.

"I don't think it advances us, that's for sure," Romar said.

The Cougars nearly routed the Huskies, starting the second half on a 14-6 run capped by a five-point possession when Romar was given a technical foul after coming on the floor and stomping his foot in anger. Casto appeared to be fouled before turning to shoot but was given continuation. Thompson hit the two technical free throws and Casto finished the possession with his free throw to push the Cougars' lead to 15. After Thompson hit a 3-pointer on the next possession, Washington State led by 17.

Washington finally arrived late, making one final charge that turned Hec Edmundson Arena into a frenzied mess of noise in the final minutes but ultimately proved too late.

"We can go on and on about what happened in the game, but just not being able to go over the hump and win," Washington's Justin Holiday said. "I do think we fought back, but we didn't fight enough."

Down 61-43, Bryan-Amaning converted a three-point play and started a 16-4 run in less than two minutes. C.J. Wilcox, Venoy Overton and Thomas knocked down 3-pointers and, mixed with a pair of Cougars turnovers, had the lead trimmed to 65-59 with 4:06 left.

Reggie Moore stemmed the run with two free throws and, after a costly Washington turnover, Casto followed up Moore's miss to push the lead back to 10 with 3 minutes left.

Overton was then called for a charge for running over Abe Lodwick in the lane, and the Huskies' chances at a remarkable comeback were finished as the Cougar chants started rising from the top of the arena.

"It was just gut-check time," Thompson said. "We don't want our season to end early. We know we're an NCAA-caliber team."