TUCSON, Ariz. - No. 3 Arizona finally caught Colorado in the final 9 seconds of regulation play, then benefitted from a controversial waived-off basket in the final second and defeated the Buffaloes 92-83 in overtime on Thursday night.

The Buffs believed they had won when senior Sabatino Chen banked in a three-pointer at the final buzzer in regulation of their Pac-12 Conference opener. But after conferring with the timekeepers and watching the replay monitor at the McKale Center, officials disallowed Chen's shot and the game went into OT.

Shown a replay of Chen's trey before his postgame interview with KOA Radio, CU coach Tad Boyle said, "That just makes me sick to my stomach . . . I'm sick to my stomach because I think our team deserved to win that game. But we didn't and we have to move on from it."

Boyle said he was proud of his team and that it "had that game won in a lot of ways." He also promised the Buffs would move on, but they also would remember: "We're not going to move on as, 'Oh, were going to forget about it and move on.' We're going to remember this because you have to remember this feeling. If it doesn't hurt in the pit of your stomach and you're not a little bit pissed off then something is wrong with you."

In the overtime, it was all Wildcats, who trailed by as many as 17 points in the first half and 16 in the second. Less than a minute into overtime, they took their first lead since 5-4 on a three-point play by Kevin Parrom to make it 83-82.

The Buffs tied it at 83-83 on one of two free throws by Xavier Johnson, who made his first career start in place of Chen. But CU didn't score again. Arizona - beaten twice by CU last season, the final time for the Pac-12 tournament title - got nine more points and rolled to its first 13-0 start since 1931-32.

The Buffs (10-3, 0-1) play at Arizona State on Sunday at 6 p.m.

Five CU players scored in double figures, topped by Askia Booker's 18. Freshman Josh Scott and Chen scored 15 each - a career-high for Chen - while Johnson had 13 and Spencer Dinwiddie 11.

Arizona's Mark Lyons, who sent the game into overtime with a pair of free throws with 9.2 seconds left in regulation, led all scorers with 24 points. He made all 10 of his free throw attempts, while CU hit 17-of-29. In the final 1:44 of regulation, holding a seven-point lead, the Buffs made only three of eight free throw attempts.

"You have to look at the free throws," Boyle said. "We shot 58 percent for the game; we got away with that earlier in the year at times but tonight we didn't get away with it, it cost us the game. And I'm not talking any one guy, I'm talking about as a team. So, you've got to look at what you can do better, and that is what we can do."

CU committed only 11 turnovers, but four of them came in the final 2 minutes when Arizona was catching up. Counting the 5 extra minutes, the Wildcats outscored the Buffs 22-5 in the final 6:44. Boyle said he thought his team "got a little soft defensively at the end. Second half they shot 60 percent from the field and we're one stop away from that game, we're one or two free throws away from that game . . .

"I asked our guys to play hard, play smart, and to play together. I thought we played hard, I thought we played together, I thought at times we didn't play smart and those are the things we have to learn as a young team on the road in an environment like this."

The Buffs, who led by 10 points with 1:53 remaining in regulation, played the extra period minus Andre Roberson. He fouled out in the final 2 minutes of regulation with nine points and 11 rebounds.

For the first time since the opening game, Boyle changed his starting lineup, inserting the 6-6 freshmen Johnson in the place of the 6-4 senior Chen. And Boyle's move paid immediate dividends as the Buffs started fast by slowing it down. CU controlled the pace and led by as many as 17 points (30-13) with 4:30 remaining in the first half.

CU pulled away with a 15-1 run, and "XJ" was instrumental in that spurt. After opening the scoring with a layup, he finished the half with 12 points, including a pair of the Buffs' six three-pointers that tied their season high. They finished 10-of-21 from beyond the arc.

But CU was certain that Arizona would snap to life, and it happened in the half's final 4:30. After their long drought (three field goals) in the opening 15 minutes, the Wildcats closed the half on a 14-4 run and trailed by only 7 (34-27) at intermission.

Helping Johnson with CU's first-half scoring load was Booker, who contributed three of the Buffs' treys and finished the half with 11 points. But a Booker miscue in the final 25 seconds also helped the Wildcats boost their momentum heading into their locker room. At the 3.5 second mark, a Booker turnover and subsequent foul sent Nick Johnson to the foul line.

He hit both free throws with 2.2 seconds showing, cutting the Buffs' lead to 34-27 and finally awakening the McHale Center crowd. But Arizona's total tied for its lowest of the season, and it matched its field goal total with seven turnovers.

The Buffs opened the second half with the same intensity as they did the first, outscoring the Wildcats 7-0 on two free throws by Scott, a three-pointer by Roberson from the right corner on an assist by Booker and a Roberson throw-down in transition on a sweet lob by Dinwiddie.

CU was up again by 14 (43-29), but the Buffs knew they couldn't rest on that margin. And other factors came into play: About 51/2 minutes in, both teams had to sit a star each. Roberson went to his bench with three fouls and Solomon Hill to his with four fouls.

After Arizona pulled to within 10 (45-35), Chen replaced Roberson and promptly contributed a conventional three-point play, then hit a trey from the left corner as the Buffs went back ahead by 16 (56-40).

The Buffs were expecting a Wildcats run, but they withstood this one. Just shy of the 10-minute mark, Chen delivered another trey to push CU up 59-49, and the Buffs held that 10-point margin until Lyons hit a layup and Hill followed with a three-pointer.

Suddenly, Arizona was within six (64-58) with just over 6 minutes left.

No sweat for Chen. He hit consecutive layups - the second on a goal-tending call - to restore a double-digit CU lead (68-58) with 41/2 to play. The Buffs kept that 10-point advantage (73-63) on a trey by Booker from the left wing with 2:47 left.

Booker hit two free throws at the 1:53 mark for another 10-point CU lead (75-65), but a traditional three-point play by Lyons pulled the Wildcats to within 75-68 with 1:49 remaining.

With 1:33 left, Arizona trimmed CU's lead to 78-73 on a three-pointer by Hill, then to 78-74 on one of two free throws by Johnson as Roberson committed a turnover and fouled out. The Wildcats caught the Buffs at 80-80 on Lyons' pair of free throws, setting up Chen's nullified three-pointer at the buzzer.

And if the replay monitor wasn't kind to the Buffs, neither was overtime.