LAS VEGAS -- Askia Booker scored 21 points and keyed a late run, leading Colorado to a 59-56 win over scrappy Southern California in the opening round of the Pac-12 tournament on Wednesday.
Their NCAA tournament hopes still up in the air, the Buffaloes could not afford a loss to the last-place Trojans.
Despite beating USC twice during the regular season, Colorado (22-10) had a hard time shaking the Trojans, unable to get much separation until going on a 13-1 run late in the second half.
USC (11-21) still had a shot at the end, but Byron Wesley's 3-pointer at the buzzer came up just short.
Josh Scott had 13 points and Xavier Johnson added 11 for the Buffaloes, who move on to face California in Thursday's quarterfinals.
Wesley finished with 23 points for the Trojans, who kept it close despite going 5 of 22 from 3-point range.
Colorado appeared to be in good shape for an NCAA tournament berth after opening the season 14-2. Things changed quickly when leading scorer Spencer Dinwiddie went down with a knee injury on Jan. 12.
The Buffaloes went 7-7 without their star guard and hurt their NCAA tournament resume by losing three of their final four regular-season games. That left Colorado teetering on the NCAA bubble and likely in need of a good Pac-12 tournament run to earn a spot in the bracket.
The Buffaloes won the Pac-12 tournament as the sixth seed in 2012, so they know firsthand it's possible.
To get their run going, they had to get past USC.
The Trojans' first season under Andy Enfield has been a struggle, with two wins in 18 Pac-12 games.
Colorado swept the two meetings with USC during the regular season: a lopsided victory in Boulder, a much tighter game in Southern California.
The Buffaloes had a hard time shaking the Trojans in the first half.
USC kept Colorado within reach despite poor shooting early in the opening 20 minutes, not allowing the Buffaloes to lead by more than six points.
Colorado led 29-27 at halftime despite hitting 13 of 25 shots and holding the Trojans to 1-of-8 shooting from 3-point range.
USC was still right with the Buffaloes in the second half, answering every time they tried to pull away, then taking a five-point lead midway through.
Booker help Colorado finally get a little bit of a cushion.
The Buffaloes' feisty point guard got them going with a three-point play, then hit a jumper and fed Johnson for a dunk in transition. Booker added a layup in transition, finishing off a 13-1 that put Colorado up 58-50 with 3 minutes left.
USC still wouldn't go away, getting a stop after pulling within three, but Wesley couldn't get his 3-pointer in transition to fall.