LAS VEGAS — Mouths agape on the bench, USC looked for answers from above during the first half of its crucial Pac-12 tournament opener against Washington.

After a timeout, shell-shocked by three straight Washington three-pointers, several USC players, chests heaving, gazed at the videoboard above the court. It did not show a friendly message: A double-digit deficit, a clocking ticking down to halftime and a reckoning with a possible early end to the season.

It made sense that in this, likely USC’s final test before an NCAA tournament bid, it would face a big deficit. USC had already come back from 10 points down 10 times this season.

Its 11th may have sent USC back to the big tournament. USC stormed back again for a 78-73 victory at T-Mobile Arena on Wednesday evening.

USC won, but did not resolve its late-game issues. Up seven points with 45 seconds left, USC avoided disaster on a missed three-pointer by Washington that would’ve tied the score.

The Trojans (24-8) advanced to the quarterfinals, where it will play UCLA here for the third season in a row.

Wednesday’s victory was the second game in a row that Washington had put a fright into USC. The start of the conference tournament obliged USC to play Washington after ending its regular season with the Huskies last week. The absence of Washington’s star, Markelle Fultz, made the task significantly easier. Fultz, considered perhaps the top prospect if he declares early for the NBA draft, was held out of both games with knee soreness.

Despite his absence, USC had slogged through an uninspired first half in the previous affair and couldn’t shake Washington until the final minutes. Throughout, they were tormented by Washington’s big man, Noah Dickerson, who scored 27 points.

There were few more answers the next time. Dickerson scored a dozen points in the first half to stake Washington (9-22) to a small lead before Matisse Thybulle’s three-pointers on three straight possessions ballooned the difference to 10 points.

After the timeout, the Trojans responded with eight unanswered points over a three-minute span to move within striking distance, 39-37, by halftime.

The game swung on USC’s defense. In the second half the Trojans swarmed Washington for 10 turnovers and turned them into easy baskets. Five minutes in, Jordan McLaughlin grabbed a loose ball, took one dribble and, without putting a second hand on the ball, whipped a pass the length of the floor like a pizza chef spinning a pie to a companion. De’Anthony Melton feasted with a dunk.

Five minutes later, Bennie Boatwright drew a foul, Washington’s Carlos Johnson was whistled for a technical and Chimezie Metu hit a turnaround to finish a six-point possession after Boatwright made all four foul shots. It was enough to overcome the sloppy close out.

Metu finished with 24 points. Boatwright scored 13.

For Washington, Dickerson finished with 18 points and David Crisp led the team with 22.

Buffaloes 73, Cougars 63

LAS VEGAS — Colorado rallied from a 14-point halftime deficit to defeat Washington State on Wednesday in the first round of the Pac-12 Tournament at T-Mobile Arena.

Colorado’s Derrick White scored 17 of his 26 points in the second half, Xavier Johnson added 19.

Colorado (19-13) got off to a miserable start at both ends as Washington State raced out to a 19-point lead. The seventh-seeded Buffaloes whittled into the lead by halftime and overtook the Cougars in the second behind White, who made 8 of 15 shots.

Colorado hit 15 of 28 shots in the second half to complete the comeback, earning a spot in today’s quarterfinals against No. 7 Arizona.

Washington State (13-18), the tournament’s No. 10 seed, lost all its mojo after a stellar first half to end the season in disappointment. Charles Callison and Ike Iroegbu scored 16 points each, and Josh Hawkinson had 12 points and 12 rebounds.

Washington State was the team looking for a blowout once the teams hit the floor in Vegas, using a 16-2 run to go up 25-9 midway through the first half.

The Buffaloes started to fight back late in the half, closing within 41-27. The Cougars hit 17-of-30 shots in the half, including five of eight from 3-point range.

Colorado picked it up even more to start the second half, hitting five of its first eight shots to pull within 45-42 in the opening five minutes. White had 13 points in that stretch.

The Buffaloes tied it at 49 and kept pushing, going up 59-52 on Johnson’s three-point play on a tomahawk dunk in transition and pulled away over the final 90 seconds.