Defending champion Connecticut, along with Houston, Purdue and North Carolina, are the top seeds in a March Madness bracket that started going haywire even before the pairings came out Sunday.

Of the four top seeds, only UConn heads into the tournament coming off a win. That played into the Huskies receiving the No. 1 overall seed. The other three top seeds lost in their conference tournaments.

Those were hardly the only surprises over the final weekend of hoops before the sport's main event hits center stage.

Unexpected titles placed teams like Oregon, North Carolina State and even Duquesne, none of whom were projected to make the field, into the field of 68 via the automatic bid that goes to conference champions. The teams they beat gobbled up a handful of the 34 at-large bids, shrinking the number of spots available to teams on the so-called bubble.

The last teams in included Colorado, Virginia and, surprisingly, Boise State, which wasn't widely considered a bubble team. Those missing out included Oklahoma, St. John's and Pittsburgh, all of whom were projected by many to make it as recently as Friday.

The tournament starts Tuesday with two First Four games, including a matchup between Virginia and a Colorado State team that few thought was on the bubble. The 32 first-round games take place Thursday and Friday. The Final Four is set for April 6-8 in Glendale, Arizona.

UConn, which opens Friday against Stetson, is the favorite according to FanDuel Sportsbook and is trying to become the first repeat champion since Florida in 2006-07. The Huskies (31-3) are on a seven-game win streak and are tied with James Madison for most wins in the nation.

“We’ve been the best team in college basketball,” coach Dan Hurley said. “Obviously, March Madness next week, who knows what goes on there, but we’ve clearly been the best program in the country this year.”

The best conference? The SEC and Big 12 placed eight teams each in the bracket, followed by the Big Ten and Mountain West with six apiece.

The shrinking bubble took its toll on the selection committee.

“This year is harder than all my previous years combined. Just gut wrenching knowing some very good teams will unfortunately not be dancing,” Jamie Pollard, the athletic director at Iowa State in his fifth year on the committee, said Saturday night on social media.