And then there was one. Just a couple of hours after overall No. 1 seed Gonzaga went down in a heap in the West Region against No. 4 seed Arkansas, No. 5 seed Houston sent No. 1 Arizona spiraling out of the South with a 72-60 victory. With the Wildcats' loss, three of the field's four No. 1 seeds have been bounced before the regional finals.
Houston (32-5) led Arizona (33-4) by six points at halftime, but pushed its advantage into double digits as the second half went on and the Wildcats failed to unlock the Cougars' defense. That became an even bigger problem as guards Jamal Shead (21 points) and Kyler Edwards (19) continued to hit key jumpers. One of those Edwards 3-pointers came with 1:26 remaining after Arizona used Houston turnovers to claw to within six points.
Together, Houston's two guards made 6-of-6 3-pointers in the second half.
The Cougars will now play No. 2 seed Villanova, a 63-55 winner over Michigan, on Saturday with hopes of reaching their second consecutive Final Four. Villanova last reached the semifinals in 2018 when the Wildcats won it all.
Houston has always looked strong in the advanced metrics and was actually a one-point favorite over Arizona entering the game on statistics website KenPom. But the Cougars were even better than that Thursday night and continued their unlikely run while playing without injured honors candidates Marcus Sasser and Tramon Mark.
Baylor was the first No. 1 seed to exit the field -- North Carolina knocked off the Bears in the second round -- meaning Kansas is the lone No. 1 seed remaining, with the Jayhawks facing their own challenging Sweet 16 contest against No. 4 seed Providence on Friday.
Since the NCAA Tournament field expanded to 64 teams in 1985, the semifinals have been played without a single No. 1 seed just twice. Here's what Houston's victory on Thursday night means:
1. Kelvin Sampson's Cougars keep pushing
Houston coach Kelvin Sampson likely didn't get enough credit in the National Coach of the Year discussions. The Cougars entered the season with one of the nation's top projected backcourts with Sasser and a rising sophomore in Mark. Sasser averaged 17.7 points per game before a toe injury knocked him out for the season in December. Mark missed the first part of the season, then hit his stride by averaging 17.3 points per game over a three-game stretch in December before he, too, was lost for the year with an injured shoulder.
That certainly opened the door for Houston's backcourt depth. Mark's sophomore classmate, Shead, has stepped into that role well. He's now averaging 17 points and 5.3 assists per game in the NCAA Tournament, while Edwards has given Houston its best scoring threat, putting up just under 20 points per game in the Cougars' three NCAA Tournament wins.
2. Houston an early favorite over Nova on KenPom
Despite being the No. 5 seed, Houston will be favored over No. 2 seed Villanova as well, according to KenPom. The website projected a 74-73 victory over Arizona, giving Houston a 51% chance to win. The early projection on Houston-Villanova again sees the Cougars as a two-point favorite, this time at 65-63, with Houston given a 57% chance to win.
With Gonzaga's exit, Houston is now KenPom's top-ranked team in the NCAA Tournament field, followed by the site's No. 5 overall team in Kansas.
3. Where Arizona goes from here
Arizona will certainly enter the offseason wondering "what if?" Even beyond point guard Kerr Kriisa battling through an ankle injury at the most inopportune time, the Wildcats made just 7-of-18 layups and were still within six points with the ball following a Houston turnover with about two minutes left. But the Wildcats gave the ball back via turnover themselves, and Edwards hit a huge 3-pointer to push the lead back to nine.
Even with Thursday night's loss, Tommy Lloyd's first season at Arizona was an unqualified success. Now, he'll wait to see what kind of roster he'll have. Bennedict Mathurin is a projected lottery pick and will likely leave Tucson. Situations could be a bit more fluid with Christian Koloko, who was one of the nation's best two-way big men but could be a borderline first-round pick right now, and with versatile wing Dalen Terry.
Should Terry and Koloko both return alongside Kriisa and Azuolas Tubelis, Arizona is staring at another top-five team and national title contender. Losing one of the two could still keep the Wildcats in the top 10-15 range depending on the other pieces, while losing both might push the Wildcats down a bit.