LAS VEGAS (AP) Arizona played a near-flawless first half, pouring in shots, shutting Colorado down, threatening to turn the Pac-12 Tournament quarterfinal into a blowout.
The momentum shifted dramatically in the second half as the Wildcats let up and the Buffaloes erased nearly all of a 22-point deficit.
The Wildcats held on to move on to the semifinals, but it was much harder than it needed to be.
Allonzo Trier scored 23 points, Ryan Anderson had 17 points and 11 rebounds, and No. 15 Arizona held off Colorado 82-78 on Thursday.
''I guess if you're the coach, you can look at it this way: Hey, everything's fine. We're in the semifinals against Oregon. Awesome job. We advanced. A lot of teams would have loved to,'' Arizona coach Sean Miller said. ''Or you can really say our effort level is as bad as I've ever seen in the last 20 minutes. I choose to focus on the second one.''
Arizona (25-7) has been plagued by inconsistency, only playing well for a half in many of its games.
Most games, the Wildcats struggle early and wear teams down late.
This time, they almost got run over.
Up 17 at halftime, Arizona watched as the Buffaloes raced past them for one offensive rebound after another - 25 in all - to chip away at the lead.
Colorado had the Wildcats on their heels and were within reach, pulling within two on George King's 3-pointer with 3 seconds left.
Arizona managed to escape, pushing the lead to four on Gabe York's two free throws, but will need to play a full game if it's going to beat No. 8 Oregon in the semifinals Friday night.
''If you hold our team to the standards of the past at Arizona or you look at us as competing for this tournament's championship, we're not going to be able to advance and be the same team that we've been,'' Miller said of his team only playing well for one half.
Colorado (22-11) clawed its way back from a huge hole by hitting the offensive glass, but couldn't overcome its shaky shooting. The fifth-seeded Buffaloes shot 34 percent and made 5 of 19 from 3-point range, leaving their NCAA Tournament fate in the hands of the selection committee.
King had 22 points, and Josh Scott finished with 16 points and 13 rebounds for Colorado, which had 26 second-chance points.
''The one thing about our team is there is no give-up,'' Colorado coach Tad Boyle said. ''They've got tremendous fight, tremendous resolve and I'm really proud of the comeback that we staged to get ourselves back in the game.''
Colorado opened the tournament with a dominating performance, beating Washington State 80-56 behind King's 21-point night.
That earned the Buffaloes a shot at the Wildcats, who were itching for a rematch after losing in Boulder on Feb. 24.
Arizona rallied from a 10-point, second-half deficit in that game, but couldn't make the plays down the stretch or stop Scott, who had a season-high 26 points.
The Wildcats turned the rematch into a rout from the opening tip.
Smothering the Buffaloes defensively, Arizona set up easy baskets in transition while opening with a 14-2 run, setting off a chant of ''U of A!''
The Wildcats kept it rolling, building a 37-20 halftime lead York's 11 points.
Colorado had more turnovers than field goals - nine to eight - and missed all six of its 3-point attempts.
''Our guys were down. They were disappointed,'' Boyle said. ''But, again, there is no quit in these guys. There wasn't any question in my mind.''
He was right.
The Buffaloes found their rhythm a bit in the second half, gaining a surge a momentum midway through while cutting into Arizona's lead.
Trier stemmed the tide briefly with a couple of athletic shots in transition, but Colorado fought back one more time, pulling to 64-57 on Scott's three-point play with 5 minutes left.
The Buffaloes kept clawing back every time Arizona tried to pull away, but couldn't make it all the way back, finishing just short.
Colorado: The Buffaloes had a 51-35 rebounding advantage. .. Colorado made 21 of 25 free throws.
Arizona: The Wildcats blocked 11 shots, including three by Anderson. ... York finished with 15 points and Kadeem Allen had 12.
Colorado has to wait until Sunday to find out if it will play in the NCAA Tournament.
Arizona faces No. 8 Oregon in the semifinals Friday night.