LAS VEGAS -- Arizona sophomore guard Allonzo Trier left the court at T-Mobile Arena, arms raised, a trophy in one hand, soaking in cheers from the fans.

His crazy journey of a season still has the most important act to come, but a moment such as this -- being the Most Outstanding Player of the Pac-12 tournament after the Wildcats' 83-80 victory over Oregon on Saturday night -- hardly seemed possible in mid-January after Arizona had already played 19 games without Trier.

A positive preseason test for a performance-enhancing drug put Trier on the bench through mid-January, even though the school had won an appeal to the NCAA. Trier, however, could not play until the banned substance was out of his system.

"I don't think we had the picture painted like this," Trier said after scoring 23 points against Oregon, including four key free throws in the final 17.5 seconds.

"Everything looked so down. But just extremely proud to be a part of this team. Extremely happy to be able to play basketball again. Something I really loved was taken away from me for quite an extended period of time. So this is just a great feeling. I appreciate every time I take the court. I don't take the game for granted at all."

Seventh-ranked Arizona had to hold off several late rallies to beat short-handed Oregon after being up by 14 in the second half.

"Our guys really, really battled back," said Oregon coach Dana Altman. "Put ourselves in a position. Our press helped us. Got us in position a couple times. ... We just didn't get it done."

Trier also had eight rebounds and led four players in double-figure scoring for the Wildcats (30-4), who are in line to stay in the West region for the NCAA Tournament, likely as a No. 2 seed behind Gonzaga.

It was a disappointing end to a devastating day for the fifth-ranked Ducks (29-5), who announced that shot-blocking forward Chris Boucher, a stretch four averaging 11.8 points per game, suffered a torn ACL in a semifinal game Friday night.

"Chris is a very talented young man, and he's a big part of our team," Altman said. "But that's part of any season. I just feel really bad for Chris. He's a wonderful young man, and it's really hard for him. It was a big blow to our team this morning. We were all kind of down, because he's one of the most popular guys on the team."

The Ducks turned up the heat in the second half with a full-court press that helped fuel their offense. Oregon cut the lead to four points on five occasions and then to 78-75 on forward Dillon Brooks' 3-pointer with 1:38 to go.

Arizona forward Lauri Markkanen made 1 of 2 free throws with 1:22 to go, and then Arizona guard Kadeem Allen drew a charge on a driving Dylan Ennis with 55.7 seconds remaining.

Markkanen and point guard Parker Jackson-Cartwright combined to miss four consecutive free throws in the final minute, allowing Oregon center Jordan Bell to cut the lead to 79-77 on a layup with 24.7 seconds to go.

That's when Trier came through.

His free throws with 17.5 seconds left put Arizona up four. Oregon guard Tyler Dorsey missed a 3-pointer from the corner. Oregon again fouled Trier, who drained two with 5.4 seconds to go.

"It has never been easy for us," said Arizona coach Sean Miller.

"We have dealt with adversity and obstacles as much as almost any group that I've been a part of, and yet we've been able to continue to climb and grow. You always hope that it comes together for you in March. Right now that's really what's happened."

Brooks scored 25 points to lead the Ducks, who beat Arizona by 27 points at home on Feb. 4 in the only regular-season meeting between the teams. Oregon made 16 of 25 3-point shots in that game but was a mere 6 of 22 from beyond the arc Saturday night.

Dorsey added 23 points for Oregon and Bell had 16.

NOTES: Arizona has appeared in 10 championship games in the 20-year history of the Pac-12 tournament. The Wildcats also won in 1988, 1989, 1990, 2002 and 2015. ... Oregon won tournament titles in 2003, 2007, 2013 and 2016. ... Oregon F Dillon Brooks entered the game with 1,511 points and then passed G Ron Lee for 11th on the school's career scoring list. ... F Keanu Pinder, a junior college transfer, made his first career start for Arizona, replacing C Dusan Ristic against the Ducks' small starting lineup. Pinder picked up three fouls in the first 5:03 of the game. ... Arizona PG Parker Jackson-Cartwright has made 23 of his last 33 3-point shots, including 2 of 2 vs. Oregon. ... Arizona G Allonzo Trier averaged 20.1 points in three tournament games.