The defending national champions are done. Done before their title defense could even really get started.

Top-seeded Villanova was upset by eighth-seeded Wisconsin, 65-62, in the second round of the NCAA tournament Saturday, the first major upset of this year’s March Madness.

Nigel Hayes, after two years of struggles on offense, won the game for the Badgers with a nifty move on the baseline with 11 seconds left to break a 62-62 tie:

Wisconsin then sealed the game with a stop on the other end.

The No. 8 seed had come back from a seven-point deficit late in the second half to tie the score. With the game knotted at 59 with two minutes to play, Bronson Koenig came off a down screen and buried a 3-pointer:

Koenig nearly turned from hero to goat on a later possession. Up one with 40 seconds to play, his weak pass was stolen by Donte DiVincenzo, who was fouled by Hayes. DiVincenzo, however, missed the second of two free throws. Hayes won the game on the other end.

Villanova, the top overall seed, went 32-3 on the season, won a fourth consecutive Big East championship, and took home the Big East tournament title a week ago. Josh Hart and Kris Jenkins came into the NCAA tournament with an opportunity to become the winningest players in college basketball history. That quest was cut short as Jenkins was held to just six points on 2-of-9 shooting.

The Badgers came in to the game hot after a run to the final of the Big Ten tournament, and, after seeing off Virginia Tech on Thursday, they stunned the Wildcats. Villanova was held to 41 percent from the field.

Wisconsin is on to its sixth Sweet 16 in seven years. The only time the Badgers didn’t play on the second weekend of the NCAA tournament since 2010 was 2013, when they lost to Ole Miss in the first round. After a late-season run of losses and a dip to a No. 8 seed, the streak looked likely to end in 2017, but Greg Gard and the Badgers have rediscovered last season’s magic.

Less than a year after Koenig beat second-seeded Xavier in the second round of the tournament with a fall-away 3 at the buzzer, the senior guard was at it again. He returned to the game with four fouls, made a 2-point jumper to bring Wisconsin within three with 4:25 to play, then tied the game with a 3-pointer with 3:28 remaining.

It was Hayes, however, who won the game for Wisconsin. Hayes has had an up-and-down career — more up early, more down lately. As a sophomore, the 6-foot-8 forward shot 54 percent from 2-point range and 40 percent from 3. But he regressed as a junior to 40 percent from inside the arc and 29 percent from outside it. His iffy jump shot made him a one-dimensional offensive player, and inhibited Wisconsin’s offense.

Hayes didn’t need a jump shot to beat Villanova, though. He only took one 3-pointer and missed it. But he was 8-for-15 from inside the arc, scored a team-high 19 points, and came through on one of the biggest drives of his career. He had attacked the rim relentlessly all season and all afternoon, sometimes successfully, sometimes unsuccessfully. His ability to bully his way through an undersized Villanova team was invaluable for Wisconsin.

The Badgers jumped out to an early lead despite foul trouble for star forward Ethan Happ. Their defense was stout. Koenig scored nine first-half points. A Hayes three-point play put the Badgers up 20-12.

Villanova came back to cut the halftime deficit to four, and made a gradual second-half charge with Koenig on the bench. The senior point guard picked up his second, third and fourth fouls early in the second half. Villanova led 57-50 with just over five minutes remaining.

Wisconsin finally regained the lead on Happ’s driving layup with 2:36 left, then needed the big shots from Hayes and Koenig to seal the upset.

The Badgers will play the winner of Florida-Virginia on Friday night in New York. Their win opens up the East regional for No. 2 seed Duke, who becomes the clear favorite to emerge from it and advance to the Final Four.

More March Madness coverage from Yahoo Sports:
• Marquette’s loss cost one Berkshire Hathaway employee $1 million
• Charles Barkley fuels on-air beef with Lonzo Ball’s dad
• UCLA star Ball suffers scary fall in win
• Watch: Who wins the Yahoo Sports ‘Seinfeld’ bracket?