Thursday’s opening day of the NCAA tournament featured several exciting games, but the unofficial start to March Madness 2018 lacked a real, major upset through 12 contests.

But when it seemed chalk would almost exclusively rule the slate, 13th-seeded Buffalo provided the long-awaited stunner. The MAC champions outplayed No. 4 Arizona from start to finish and crushed Sean Miller’s club 89-68.

And was it ever a masterpiece.

Buffalo played an outstanding defensive game and clearly tried to force anyone other than Deandre Ayton and Allonzo Trier to propel Arizona. As the final score suggests, that wasn’t close to happening.

The Wildcats finished a brutal 2-of-18 from three-point range, including an 0-of-5 mark from Trier. The junior guard constantly forced the issue, driving into traffic but finding nowhere to go. No teammate provided a spacing threat, and he typically couldn’t throw it to Ayton, either.

Buffalo refused to give the potential No. 1 NBA draft pick favorable post-up opportunities, fronting him in the post while providing help over the top. Ayton still recorded 14 points and 13 rebounds, but the Bulls limited his impact.

Most of all, though, Buffalo shredded a lifeless Arizona defense.

“We got high-major players on our team,” Buffalo coach Nate Oats said following the victory on the CBS broadcast. “So it’s not like we’re a bunch of mid-major kids. We’ve got some really good players—they played their tail off.”

Wes Clark poured in 25 points on 10-of-14 shooting and dished seven assists, and Jeremy Harris provided 23. CJ Massinburg and Nick Perkins combined for 32 points thanks to an 8-of-14 performance beyond the arc. Overall, the Bulls connected on 15 threes at a 50 percent rate.

When one team musters six points from long range and the other tallies 45, there’s a good chance a 21-point margin of victory will happen.

Simply, as Brian Bennett of The Athletic noted late in the second half, Buffalo deserved every bit of the emphatic win.

When Arizona trimmed the lead to 60-55 midway through the second half, it seemed the upset was on the verge of falling apart. Instead, Buffalo demanded control.

Perkins hit two free throws. Dontay Caruthers swiped the ball from Rawle Alkins and found a wide-open Harris for three. Massinburg banked home a triple. Within about two-and-a-half minutes of the Wildcats threatening, the Bulls had extended their edge to 14.

From there, Buffalo flat-out broke Arizona.

The Wildcats failed to score during a three-plus-minute stretch. And after the drought-breaking bucket, Harris responded by draining a step-back jumper in Ayton’s face.

From 9:21 to 1:02 remaining, Arizona managed just six points. That late-game execution is what separated Buffalo from the almost-stunners scattered throughout Thursday’s slate.

In 16 games, 13 favorites defended their billing. Beyond the Bulls, the only other underdogs to win—Loyola-Chicago and Alabama—had spreads of 2.5 points or fewer, according to OddsShark. Those can’t be classified as shocking results.

Plenty of challengers were close, but every one of those upset bids fell apart down the stretch.

No. 13 seed UNC Greensboro held a 64-62 advantage with less than a minute to play before No. 4 seed Gonzaga scored six straight to win. Penn put a scare into top-seeded Kansas but coughed up a 10-point lead.

South Dakota State, one of the most popular 5/12 upset picks, surrendered an 11-3 run to Ohio State in the closing two minutes. Fellow No. 12 seed Davidson was within two points of Kentucky entering the last three minutes but trailed 76-65 with 20 seconds left.

Although No. 14 seed Stephen F. Austin led third-seeded Texas Tech 57-55 as the clock ticked below five minutes remaining, the Lumberjacks folded. Montana, another No. 14 seed, scored 10 straight points to begin its clash opposite Michigan but lost by 14.

For good measure, No. 10 seed Oklahoma lost in overtime, and No. 11 seed San Diego State watched a potential game-winning three at the buzzer ricochet off the side of the rim.

Without Buffalo throttling Arizona, Thursday could’ve been viewed as an exciting series of results lacking an underdog appeal. As enjoyable as close finishes are, many watch the Big Dance looking to fall in love with a Cinderella and jump on bandwagons.

Thanks to a dominant effort—particularly in the second half—the Bulls provided that memorable upset over Arizona.

And perhaps most importantly, Buffalo made one thing clear: After a chaotic day full of “almost,” the madness has arrived.

Stats via Sports-Reference and NCAA.com unless otherwise noted. Follow Bleacher Report writer David Kenyon on Twitter @Kenyon19_BR.