The Buffs began what their head coach described as "the most important weekend of the year" with the most disappointing performance of the Tad Boyle era.
Colorado was cold on offense and a no-show on defense during a deflating 74-50 loss to Stanford on Thursday night in front of near capacity crowd of 11,036 at the Coors Events Center.
The Buffs' (18-9, 10-5) dreams of a Pac-12 regular-season title are probably dashed after the nightmarish performance.
CU, alone in third place entering the game, dropped into a tie with Oregon (10-5) for fourth behind Cal (13-3), Washington (12-3) and Arizona (11-5).
"I feel like our fans that came out tonight got cheated," Boyle said.
The Cardinal (19-9, 9-7) had lost six of nine games since thrashing the Buffs 84-64 on Jan. 14 in Palo Alto.
Stanford dominated from start to finish and led by as many as 29 points (57-28) in the second half.
Before the game, CU was the only unbeaten team at home in Pac-12 play (7-0) and had a 13-1 overall record at the Coors Events Center.
After the game, Boyle issued an apology.
"We let a golden opportunity slip by, and one we'll never have back again, at least this year," said Boyle, who had CU in position to make a run at the program's first conference title since 1968-69. "Our fans that showed up and have been following and supporting this team all year long deserve more than what they got tonight from the Buffs. For that I feel bad and I apologize."
Askia Booker (12 points) was the only player to score in double figures for the home team. The freshman guard did most of that work when the majority of the fans had already escaped to the parking garage.
"It's disappointing. I think as a team we let our offense get to our defense," said Booker, who was 4-for-11 from the field and 3-for-6 from the line. "Shots weren't falling, and I think that transferred to our defense."
All 15 Stanford players that made the trip saw action with 11 of them scoring. RandleChasson led the way with 20 points on 7-for-10 shooting.
CU was out-rebounded 50-26 and allowed the visitors to score 17 second-chance points and to shoot 50 percent (9-for-18) from behind the arc.
"I think this is a great win for us," Stanford head coach Johnny Dawkins said. "They are a great team and are well coached. They've been having a terrific season, and we just wanted to come out and try to compete with them here in such a great environment."
The Buffs trailed 40-20 at halftime after shooting 20.7 percent (6-for-29) from the field and allowing Stanford to knock down seven 3-pointers.
That was CU's fewest points scored and most allowed all season in a first half.
Chasson and John Gage outscored the home through the first 20 minutes.
The Buffs missed their first seven shots before a Nate Tomlinson 3-pointer cut the early deficit to 9-4. After Booker knocked down a 3-pointer, CU went 6:58 without a field goal.
The Cardinal seized control of the game and kept the crowd muted with a 12-0 run to make the score 25-8.
Stanford took its largest lead of the half, 40-18, after Chasson converted a layup on a set play out of a timeout with 56 seconds left before the break.
"I don't know if we were nervous coming into the game, if we were too excited or what the deal was," senior forward Austin Dufault said. "For whatever reason, we just got down on ourselves the first two minutes of the game when we couldn't score. Instead of locking in and defending and rebounding, we just kind of folded and they really took it to us."
The Buffs will try to redeem themselves against first-place Cal on Sunday in the final regular-season game of the season at the Coors Events Center.