SEATTLE – The Pac-12 Women's Basketball Tournament trophy will not be returning to Troy this year, thanks to a 75-63 Colorado win over the defending champion USC Trojans on Thursday at KeyArena.

Behind suffocating defense and a diversified offensive attack, the Buffs avenged two regular-season losses to the Trojans and move on to Friday's quarterfinals, where they face last year's runner-up and this year's No. 1 seed, Oregon State, Friday at 6 p.m. PT on Pac-12 Networks and Pac-12 Now.

Colorado's stingy D held the Women of Troy to just 8-for-35 shooting in the first half, translating to a paltry 22.9 percent. The Trojans made only one of their five three-point attempts.

The Buffs' offensive attack was equally impressive in the first period. They shot a lights-out 14-of-24 from the field and made all nine of their free throw attempts. Their ball sharing paved the way, resulting in an assist on nine of CU's 14 made shots to carry a 39-27 lead into the break.

"I thought it was one of our better games of the season," Colorado head coach Linda Lappe said. "We're a really close-knit team and you could see that tonight in how we shared the ball offensively and how we defended."

Jamee Swan paced Colorado with 11 points, four rebounds and three blocks in the first 20 minutes, but it was her intensity, physical play and willingness to dive after loose balls that seemed to spark the Buffs. And she knew she had to bring it tonight.

"We talked a lot this week about being tough and playing Colorado basketball," Swan said. "We just needed to be tough and play as hard as we could and not let their play affect us."

With 13:02 to play in the first half and CU down 12-11, Swan swatted two USC shots in one possession, the second of which fueled a Haley Smith transition layup that gave the Buffs a lead they would not relinquish.

"Jamee played like an All-Conference player tonight," Lappe said. "I thought she did a nice job of letting the game come to her. She really was a presence in the paint and blocking shots."

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USC head coach Cynthia Cooper must have lit a fire under her squad at halftime, because the Trojans came back from the lockerroom attacking the rim and playing a physical brand of basketball. They cut the lead to as little as six at one point, but the resilient Buffs always had an answer.

"It was a strong message at halftime," Cooper said. "We talked about our defense. We talked about getting deflections and steals and rebounding the ball so that we could get out on our fast break."

With 13:05 left and the Trojans sneaking back into the game down only 47-41, Lauren Huggins stepped in front of a Kristen Simon pass and went coast-to-coast for a layup that brought the lead back to eight.

Colorado began to pull away after that steal and finish. Lexy Kresl drove for two, then after a USC shot clock violation, Huggins buried a deep three to push the lead to an insurmountable 56-43. From there, it was smooth sailing into Friday's Pac-12 Women's Basketball Tournament quarterfinal showdown with the regular-season champs, Oregon State.

The hot shooting and ball distribution continued in the second half for the Buffs. As a team, they shot 53 percent (25-of-47) and dished out 17 assists. Haley Smith finished as the leading scorer with 16 points. Huggins, who started off on the bench, made all four of her shots and finished with 11 points.

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The Trojans limped to a 29 percent shooting percentage and recorded only six assists – three coming from Brianna Barrett, who led USC in scoring with 18. The Trojans missed 10 free throws on the night.

For USC, the loss ends a tough season. After winning the tournament a year ago, the Trojans finished the 2014-15 regular season at 15-14 (7-11 Pac-12).

"I think this is a learning experience for a lot of us," Trojan sophomore Jordan Adams said. "We're going to use this going forward and hopefully have a better season next year."

The Buffs will surely be underdogs against the 26-3 Beavers on Friday, but another strong inside-outside, defense-leading-to-offense performance could be kryptonite to Oregon State.