LAS VEGAS – Arizona held off a late Oregon surge to beat the Ducks 83-80 and capture its second Pac-12 Tournament title in three seasons and a likely spot in the NCAA’s West Region tonight at T-Mobile Arena.

Allonzo Trier hit four free throws in the final 17 seconds left to clinch the win, leading the Wildcats with 21 points and eight rebounds.

It was Arizona’s second Pac-12 Tournament title in the past three seasons, and snapped a streak of three painful losses to the Ducks, who thumped UA in Eugene earlier this season, edged them in last season’s Pac-12 Tournament semifinal and snapped UA’s 49-game homecourt win streak in January 2016.

The win moved Arizona to 30-4 overall and likely earned the Wildcats a spot in the NCAA’s West Region and No. 2 seed. UA is expected to open with NCAA Tournament games in Salt Lake City and, if it wins two, would advance to San Jose for Sweet 16 and Elite Eight games if placed in the West.

BOX SCORE: Arizona 83, Oregon 80

Oregon dropped to 29-5. The Ducks are expected to get a No. 2 seed in another region, though the NCAA selection committee could downgrade them further because of the loss of forward Chris Boucher.

Boucher tore his ACL on Friday against Cal and kept playing, though the Ducks announced an hour before the game that he was out for the rest of the season.

Without Boucher, the Ducks leaned heavily on leading scorer Dillon Brooks (25 points) in the first half and never fully recovered, though they trimmed a 14-point UA lead down to just two in the second half.

Oregon shot 51.7 percent in the second half after making just 34.5 percent from the field in the first half.

The Ducks made it interesting in the final minutes and two missed free throws each from normally reliable shooters Lauri Markkanen and Parker Jackson-Cartwright only heightened the tension inside the Pac-12 Tournament’s new arena.

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Their misses gave Oregon a chance to pull within a basket, 79-77, when Jordan Bell put back a rebound with 23 seconds left. But the Wildcats managed to break the Ducks’ furious full-court press and Trier was twice fouled, and hit the four final free throws.

After Arizona held a six-point lead at halftime and went up by 14 into the second half, Oregon began to pull closer when it was able to find better offensive balance and shoot better.

The Ducks closed within four points, 60-56 after Dylan Ennis stole the ball from Markkanen as the UA freshman tried to go up for a shot under the basket – and then Ennis drove coast-to-coast for a layup.

The game stayed close the rest of the way, with Chance Comanche giving Arizona a 74-66 lead entering the final four minutes.

Arizona went ahead by 14 points, 49-35, when Allonzo Trier sank a 3-pointer with 15:22 left. But the rest of Oregon’s offense began to heat up. Tyler Dorsey picked up a foul from Kadeem Allen on a 3-point attempt and hit all three free throws to make it 49-39 and Kavell Bigby-Williams blocked a shot from Dusan Ristic that fed into a layup by Dylan Ennis.

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Bigby-Williams, who was getting a bigger opportunity with Boucher out, blocked 211 shots last season while becoming the junior college player of the year at Gillette (Wyo.) College.

Brooks led Oregon with 25 points.

In the first half, Brooks scored 17 points but was pretty much a one-man band while the Wildcats took a 35-29 halftime lead.

Oregon shot just 34.5 percent before halftime and the Ducks other than Brooks shot just 5 of 17 from the field. Brooks was 5 of 12 while hitting all six free throws he took.

Oregon had shot a blistering 65.2 percent against Arizona in its 85-58 blowout win over the Wildcats on Feb. 4 in Eugene.

Arizona made half its 26 shots from the field in the first half, but made just 2 of 9 3-pointers. Trier led UA with 10 points and five rebounds while Kadeem Allen had seven points and six rebounds.

The winner was expected to be placed in the NCAA West Regional, possibly with the No. 2 seed and opposite likely top seed Gonzaga. The loser could also get a No. 2 seed but in another region.

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In any case, UA is expected to play its first weekend games in Salt Lake City because of the tourney’s pod system for first- and second-round games.

Arizona built an eight-point lead with six minutes to go in the first half but Oregon cut it to 30-26 when Kavell Bigby-Williams drove inside for a dunk and picked up a foul from Dusan Ristic with 3:36 to go. But UA held a lead for the final 10 minutes of the game.

Possibly because he was trying to avoid having Markkanen guard Brooks – and the danger of foul trouble against the slippery Pac-12 Player of the Year – UA coach Sean Miller started junior Keanu Pinder at power forward.

However, while Markkanen was free to then cover Oregon center Jordan Bell, the move appeared to backfire: Pinder had three fouls and two turnovers in the first five minutes, including a botched inbounds pass that turned into a basket by Oregon’s Tyler Dorsey.

But while Dorsey’s bucket gave the Ducks an 8-4 lead, UA went on to lead by up to four points in the half, getting a 3-pointer and 1 of 2 free throws from Trier to take an 18-14 lead with 8:50 to go.

Brooks responded with a 3-pointer to pull Oregon within a point entering the final eight minutes of the half.

An hour before the game, Oregon confirmed that Boucher was out for Saturday’s game and the rest of the season with a torn ACL.

Boucher is the Ducks’ third-leading scorer (11.1 points) and second-leading rebounder (6.1), and is a notably tough matchup for opponents because of his size, athleticism and perimeter shooting ability.

Boucher hurt his knee in the first half of the Ducks’ Pac-12 Tournament semifinal win over Cal on Friday but continued to play. He scored 12 points while hitting 2 of 4 3-pointers and had four rebounds against Arizona in Oregon’s 85-58 win on Feb. 4 in Eugene.