Arizona came into Thursday's matchup against Buffalo as the clear favorite sitting as the No. 4 seed in the South Region, but the Wildcats walked away with a big loss failing to advance to the next round of the NCAA Tournament. 

In a huge upset on the opening day of the tournament, Arizona fell to No. 13 seed Buffalo in an ugly 89-68 loss. The Wildcats held on for much of the game, but the Bulls took a 40-38 lead at halftime and really started to pull away down the stretch growing the lead to as many as 15 points with less than two minutes remaining.

The win for Buffalo marks the first time the Bulls have won a game in the tournament, and it also means the Pac-12 is now done in the tournament. It's the first time since 1986 that the conference went winless in the NCAA Tournament as Arizona, Utah and Washington all lost their opening games this year.

Many thought Buffalo would have trouble guarding Arizona's 7-1 center Deandre Ayton, but that didn't prove to be the case despite the fact the Bulls don't have a single seven-foot player on their roster.

In what would have been a marquee matchup in the second round between Kentucky and Arizona, Buffalo will now be the team facing No. 5 seed Kentucky Saturday, who beat No. 12 seed Davidson 78-73.

Here are three takeaway's from Buffalo's win: 

1. Buffalo figured out how to stop Deandre Ayton — One reason to attribute the Bulls' success was the constant double-teaming and pressure they put on Deandre Ayton. Buffalo's defense was strong as they rushed to defend Ayton keeping multiple players on him at all times, and when he was able to get the ball, he wasn't able to sink his shots as a result of their defense. Ayton's production was reduced to 14 points on 6-of-13 shooting.

2. The Wildcats didn't capitalize from 3-point range while the Bulls did — Buffalo's win could boil down to their success behind the 3-point line. The Bulls shot 54 percent from the field, but more impressive than that was the fact they were able to hit 13 3's on 30 attempts. Two of the Bulls' leading scorers all season Wes Clark and Jeremy Harris led the way, each making three 3-pointers while CJ Massinburg had five.

3. Arizona couldn't figure out how to rebound — The Wildcats could not come up with rebounds, and in the first half, Buffalo out-rebounded Arizona. Buffalo finished up the first half with 19 rebounds to Arizona's 13, but at one point they had a 16 to 9 advantage. Overall, Buffalo proved to be quicker, faster and more aggressive.