LAS VEGAS -- The Arizona Wildcats barely survived the opening game of its revenge tour through the Pac-12 Tournament.

Allonzo Trier scored 23 points, Ryan Anderson had 17 and No. 15 Arizona's big first half was just enough to keep the Colorado Buffaloes at bay en route to an 82-78 victory in the quarterfinal game Thursday.

The Buffaloes whittled a 20-point second-half deficit to two in the final seconds.

"I think it was an eye-opener for some of the younger guys and some of the older guys who haven't been in this position before," said Arizona senior center Kaleb Tarczewski.

"I mean, this is March. Every team is a great team. There are great players and there are great coaches, and you have you to be on it or you're done.

"We had a great first half, and in the second half, I think some guys were kind of playing the scoreboard. We got comfortable."

Colorado was 1-0 against Arizona in the regular season, as was the Wildcats' semifinal foe -- top-seeded Oregon. If Arizona reaches the final, it could face Utah, which also was 1-0 against the Cats.

Arizona (25-7) was just relieved to escape after allowing 58 second-half points.

"I really was excited about our team at halftime," said Arizona coach Sean Miller. "Thought the defense was as good as it's been all year."

The game looked like a laugher early in the second half -- Arizona up by 20 -- but Colorado rallied almost all the way back, mostly thanks to a relentless effort on the glass that netted 25 offensive rebounds against the Pac-12's top rebounding team.

"The one thing about our team is there is no give-up," said Colorado coach Tad Boyle. "Look, we out-rebounded them 51-35. When you out-rebound Arizona by 16, it says something about our fight and our toughness."

Colorado guard Josh Fortune hit a 3-pointer after an offensive rebound to make it 78-74, but Arizona guard Gabe York responded with two free throws with 19.3 seconds left.

York later missed a pair and guard George King gave the Buffaloes a last gasp with a 3-pointer with two seconds left to make it 80-78. York then put the game away with two free throws.

Arizona can point to its free-throw shooting as a key reason for the win. The Wildcats were 30 of 38 in the second half.

Arizona will face Oregon on Friday night at the MGM Grand Garden Arena, which has always featured a partisan and vocal Arizona crowd since the tournament moved to Las Vegas in 2013.

The Ducks won the only regular-season meeting on Jan. 28 in Tucson, ending Arizona's 49-game home winning streak, which was the longest in the country.

"We had a difficult time guarding them in Tucson, and I think a lot of teams that have played Oregon have fallen into that category," Miller said.

Colorado (22-11) is expected to land an NCAA Tournament at-large bid.

"The short answer is yes," Boyle said when asked if he thought his team's resume was good enough. "The realistic answer is it doesn't matter what I think."

Trier scored 15 points in the second half for his eighth 20-point effort of the season. Anderson added 11 rebounds.

King scored 22 points for Colorado. Center Josh Scott had 16 points and 13 rebounds.

Arizona raced to a 13-2 lead with 14:20 to go and Colorado didn't have anyone other than Scott score until Xavier Talton hit two free throws with 7:53 left to cut the lead to 17-8.

"Man, I wish we could get it back," Colorado forward George King said of the slow start, "but I don't have a time machine or anything."

The Wildcats kept the heat on, going up by as much as 22 on a 3-pointer by guard Kadeem Allen to make it 33-11 with 3:46 left in the half.

Arizona led 37-20 at the break.

NOTES: Arizona senior C Kaleb Tarczewski became the winningest player in school history, passing former G Matt Muehlebach by playing in his 110th career victory. Arizona G Gabe York has 105 career wins. ... Colorado is 1-4 against ranked teams this season, with its lone win at home against Arizona on Feb. 24. ... Arizona's 83-75 loss to Oregon is the team's largest margin of defeat in the past three-plus years. The Wildcats haven't lost by double digits since an 89-78 setback at USC on Feb. 27, 2013. ... Former Arizona G Salim Stoudamire, who will be inducted into the Pac-12 Hall of Honor on Saturday, attended the game.