For at least one game, the UCLA men’s basketball team showed it can get by without the Pac-12 Conference’s top defender.

To the dismay of defense-first Bruins head coach Mick Cronin, however, it was early offense that bailed the conference tournament’s top seed out from an quick exit Thursday until the defense settled in late.

Freshman guard Amari Bailey scored a career-high 26 points to lead UCLA to an 80-69 quarterfinal win over No. 9-seeded Colorado at T-Mobile Arena in Las Vegas.

The 6-foot-5 guard’s performance made up for an uneven performance from a defense ranked second in the KenPom ratings, but was playing its first game without Pac-12 defensive player of the year Jaylen Clark.

Bailey made 8 of 12 shots from the field and the Bruins (28-4) were 24 of 31 at the free-throw line. Tyger Campbell added 18 points and seven assists, Jaime Jaquez Jr. chipped in 16 and Adem Bona had 11 to round out four double-figure scorers.

Bona, who had a double-double with 10 rebounds, made his biggest contribution on defense with three blocks to match his career high.

The Buffaloes (17-16) tested UCLA’s defense, making 10 3-pointers to turn most of the contest into a back-and-forth affair. Tristan Da Silva had 16 points and six rebounds to pace Colorado.

The Bruins advanced to Friday’s 6 p.m. semifinal and will play No. 4-seed Oregon, which held off No. 5-seed Washington State 75-70.

Trailing 10-5 early, the Bruins went on an 8-1 run sparked by a full-court press defense to pull ahead. From there, the shot-making picked up considerably for both teams.

Bona picked up his second foul with more than four minutes left in the half, and the Buffaloes rode their hot shooting to 38-37 halftime lead.

Colorado was 7 of 12 on 3-pointers at the break.

The Buffs were still shooting well nearing the midway point of the second half until Bona’s work on both ends helped spark a 9-0 run capped by a David Singleton 3-pointer. That put the Bruins up 55-49 with 10:49 to play.

Colorado did not go away, though, briefly pulling in front 61-60 with 5:18 left after one of Da Silva’s three 3-pointers.

Jaquez Jr., who scored 11 second-half points, answered with his own 3 on the next possession. That sparked a 9-0 run capped by four Bailey free throws to put the Bruins ahead for good at 69-61 with 3:22 remaining.

After Colorado cut the deficit to 69-65, UCLA scored the next 10 points to push the advantage to 14 points inside the final minute.

Bailey had it going early, with 12 first-half points to lead everyone at the break.

His production was particularly important in keeping pace with Colorado’s hot start. With Jaquez Jr., the Pac-12 player of the year, the focus of the Colorado defense, Bailey took advantage.

Bailey’s previous personal-best was 24 points in a win at Oregon State on Feb. 9.

Clark’s absence was felt immediately, with UCLA unable to consistently get deflections and force turnovers early.

While the Bruins had issues staying in front of their man without their best lockdown defender, there was Bona to protect the rim and alter shots when he wasn’t sending them back.

Bona blocked three shots on five other occasions earlier this season.

His performance on the boards also secured the first double-double of his career. What a time to do that, right?

None of Bona’s blocks were more breathtaking than this one in the second half:

The fabulous first-year duo of Bailey and Bona didn’t look like freshmen in their first postseason game.

Yes, it’s not the big tournament but it was still a tremendous test given all the previously stated circumstances. On top of it, the Bruins outlasted the Buffs in a contest that had 17 lead changes.

It’s still a work in progress, but the ceiling for the Bruins is as high as Bailey and Bona both grow to support Campbell and Jaquez Jr. On this day, the starting roles were reversed.

UCLA did eventually get better on defense later in the contest. Colorado had nine of its 15 turnovers in the second half and the Bruins had 24 points off turnovers for the game.

The Bruins also had a 33-27 edge in rebounds, with a 10-5 advantage on the offensive glass.

Starting five

PG Tyger Campbell: 18 pts on 4/11 FGs (1/3 3-ptrs), 2 rebs, 7 asst, 3 stls

G Amari Bailey: 26 pts on 8/12 FGs (2/3 3-ptrs), 3 rebs, 3 asst, 1 stl

G David Singleton: 6 pts on 2/8 FGs (2/8 3-ptrs), 2 rebs, 2 asst, 2 stls

G/F Jaime Jaquez Jr.: 16 pts on 5/11 FGs (1/3 3-ptrs), 9 rebs, 2 asst, 1 stl

F/C Adem Bona: 11 pts on 5/8 FGs, 10 rebs, 1 asst, 3 blks

Bench

G Will McClendon: 0 pts on 0/3 FGs (0/1 3-ptrs), 4 rebs, 3 asst

G Dylan Andrews: 1 pt on 0/1 FGs (1/2 FTs), 1 reb, 1 asst, 1 stl

F Mac Etienne: 2 pts on 1/1 FGs, 1 stl

G/F Abramo Canka: No stats

F/C Kenneth Nwuba: DNP (coach’s decision)

G Russell Stong: DNP (coach’s decision)

F Logan Cremonesi: DNP (coach’s decision)

G Jack Seidler: DNP (coach’s decision)

G Jaylen Clark: DNP (lower leg, not with team)

F Evan Manjikian: DNP (inactive, right arm)