Without the services two of its top three scorers, Colorado fought but fell to No. 10 Arizona, 68-54.
"I'm really happy with the way we battled. I thought our competitiveness and our competitive spirit was great tonight," head coach Tad Boyle told AM-850.
Xavier Johnson (ankle) and Josh Scott (back) both missed Thursday night's game with injuries, forcing Tre'Shaun Fletcher and Dustin Thomas into the starting lineup.
CU jumped out to a 9-4 lead, but Arizona responded with an 11-0 run to claim a 15-9 lead, forcing Boyle to take a timeout.
Another Wildcats run towards the end of the first half led to a 35-25 deficit at the half, despite outshooting Arizona in the first 20 minutes.
The Buffs continued to fight in the second half. After a Jaron Hopkins dunk featuring a beautiful behind-the-back assist from Dustin Thomas, Colorado found themselves down by just five, 37-32.
Arizona stretched the lead back into double digits, but at the 11:29 mark, another dunk by Hopkins cut the Wildcats' lead to five again, 47-42.
CU was never able to get closer than five in the second half.
Booker's career-high 30 points kept Colorado in the game, going 6-of-9 from downtown, and 11-of-17 from the floor.
"I thought he played with unbelievable passion and fire and competitiveness," Boyle said of his senior guard from Los Angeles. "He was terrific."
With the availability of Scott and Johnson in doubt, Colorado returns to action on Saturday afternoon at Arizona State.
"We've got Arizona and Utah, the two toughest teams on the road, in the rearview mirror," said Boyle. Now we're four games into an 18 game schedule, so we've got 14 games left, and the two hardest out of the way. We can start making some hay and making a move, but it's got to start on Saturday."