Colorado’s Sabatino Chen banked in a 3-pointer at the end of regulation but officials waved it off after reviewing the video, saying the ball was on his fingertips as the backboard lights went on to show time had expired.
Arizona (13-0, 1-0) outscored the Buffaloes 10-2 over the final 1:35 of regulation to force the overtime. The Buffaloes missed four of six free throws in that stretch.
The Wildcats were down by 17 points in the first half and 16 with 12:40 to go in regulation.
It was the third close win for the Wildcats, who beat Florida 65-64 on Mark Lyons’ layup at the buzzer and San Diego State 68-67 on Nick Johnson’s blocked shot.
Askia Booker led Colorado (10-3, 0-1) with 18 points.
Arizona’s 13-0 start is the second-best in school history and best since the Wildcats won their first 16 in 1932-33.
But they survived this one by a fraction of a second.
Chen scored a career-high 15 points, 12 in the second half. Josh Scott scored 15 points and Xavier Johnson had 13 for the Buffaloes, who beat Arizona by two points to win the Pac-12 tournament last season.
Lyons overcame an awful start to score a season-high 24 points, including two free throws that tied it at 80 with 9.2 seconds left in regulation.
Solomon Hill scored 15 points for the Wildcats. His 3-pointer with 1:35 to go in the second half cut the lead to 78-73.
No. 2 Michigan 94, Northwestern 66
EVANSTON, Ill. — Trey Burke scored 23 points, Tim Hardaway Jr. added 21 and No. 2 Michigan pounded Northwestern 94-66 on Thursday night to remain unbeaten.
Off to their best start since they opened the 1985-86 season with 16 wins, the Wolverines (14-0, 1-0) had no trouble in the Big Ten opener after breezing through the non-conference portion of their schedule.
They built a 21-point halftime lead with Burke and Hardaway Jr. leading the way and were never challenged by Northwestern (9-5, 0-1).
Jared Swopshire and Kale Abrahamson each scored 11 points for Northwestern, but the Wildcats gave up the most points they have allowed this season.
No. 10 Gonzaga 78, Pepperdine 62
MALIBU, Calif. — Elias Harris scored 18 points and Kelly Olynk had 16 to lead No. 10 Gonzaga to a 78-62 victory over Pepperdine on Thursday night in the a West Coast Conference opener for both teams.
Olynk scored 14 points in the second half as the Bulldogs (14-1, 1-0 WCC) won despite shooting a season-low 43.4 percent from the field. Reserve guard David Stockton added nine points and four steals and Kevin Pangos scored nine points.
Pangos gave Gonzaga the lead for good at 38-36 on a 3-pointer and the Bulldogs pulled away to their 23rd consecutive win against Pepperdine, its longest streak against a conference opponent.