TUCSON, Ariz. -- By a fraction of a second, the Arizona Wildcats are still unbeaten.
Colorado's Sabatino Chen banked in a 3-pointer at the end of regulation, but officials waved it off after reviewing the video and the third-ranked Wildcats went on to win 92-83 in overtime on Thursday night.
Some replays indicated the shot was taken in time. Others showed that perhaps it wasn't.
"It came down to fingertips, maybe," Chen said.
"We have a great group of guys but we can get a lot better," Johnson said. "We've escaped with some tough wins but we're going to go back to practice and get better."
This one -- in the Pac-12 opener for both -- was the most improbable of all. Arizona (13-0, 1-0 Pac-12) outscored the Buffaloes 10-2 over the final 1:35 of regulation to force overtime. The Buffaloes (10-3, 0-1) missed four of six free throws in that span.
"We would have gotten what we deserved if we had lost," Arizona coach Sean Miller said.
When Chen banked in the 3-pointer, it looked like that would be the outcome. But after huddling for several minutes, the officials said no. Referee James Breeding told a television announcer that the ball was on Chen's fingertips when the lights around the backboard went on.
"If it's the wrong call, I'm really, really sick to my stomach," Colorado coach Tad Boyle said, "because we had guys in this locker room that deserved to win that game."
Arizona 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.
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.
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.
Nick Johnson stole the ball from Andre Roberson and was fouled. Johnson made one of two free throws to cut it to 78-74 with 1:15 to play.
Scott made one of two free throws to make it 79-74 with 1:13 left. Lyons missed but Booker threw the ball away to Arizona's Jordin Mayes, whose layup cut the lead to 79-76 with 51 seconds on the clock.
Spencer Dinwiddie could make just one of two free throws with 44 seconds to go and it was 80-76. Lyons' driving layup cut it to 80-78 with 27 seconds to go.
Jeremy Adams was fouled and missed both free throws, then Lyons drove to the hoop, was fouled by Johnson and made both free throws as the crowd went crazy with 9.2 seconds left.
They fell silent when Chen banked in the shot at the end of regulation. But officials huddled around the monitor for several minutes before ruling the shot no good.
Parrom scored the first five points for Arizona in the overtime. His three-point play made it 83-82, the Wildcats' first lead since it was 5-4.
"We're playing with fire with the way that we're playing offense," Miller said. "We have talented players and we're trying to score against good defenses in January on the first three passes of a possession. It doesn't work that way."
Arizona made just 3 of its first 17 shots, going 9:40 without a field goal in the first half. When Roberson hit a 3-pointer from the corner on an out of bounds play as the shot clock expired, the Buffaloes led 30-13 with 4:37 to go in the half. Arizona had not trailed by more than 11 points this season.
Consecutive 3-pointers by Parrom and Grant Jerrett finally ended the drought and the Wildcats finished the half on a 14-4 run to cut Colorado's lead to 34-27.
But the Buffaloes regained command in the second half and led 56-40 on Chen's 3-pointer with 12:40 left in regulation.
"I'm proud of our team. I can't fault their effort," Boyle said. "We played a tough team on the road and we did what we had to do to win."