On average, 1.3 5-seeds fall each year in round one

We know a 12-5 upset is out there, we just don't know which one.

Will it be Wisconsin-Milwaukee over Alabama in Cleveland? Could it be New Mexico over Villanova in Nashville? What about George Washington over Georgia Tech or Old Dominion over Michigan State?

It's bound to happen, right? It has to, because 26 of them have occurred since the field expanded in 1985 – the most prevalent of any bracket pairing outside of the 8-9 and 7-10 games.

"That stat [5 vs. 12] means absolutely nothing once the game starts, because the quality of the 12 is so good," said Providence coach Tim Welsh, an "upset" victim to No. 12 Pacific in 2004.

But what is it about the No. 5 seed that makes it so vulnerable and the No. 12 such a hot pick?

"The 12 is usually a mid-major team from a mid-major conference that's playing well at the time," Welsh said.

"The five could be a team from a high-major conference that has dipped that isn't playing as well," he added. "We dropped to a five. In the weeks leading up to that we were looking at a three or a four and then we got beat going into the tournament. Pacific had won 15 in a row and they were playing very, very well. We were a 12 once when I was at Iona coaching, and you know when you're the 12 everybody wants to pick you to pick that upset."

Florida coach Billy Donovan knows all too well about being the No. 5 upset victim. He nearly was in 2000, when Mike Miller's buzzer-beater took out No. 12 Butler. But then in 2002, Creighton took out Florida in a 12-5 game, and it happened again last season when Manhattan beat Florida.

"I was never thinking about it, because I knew those 12s were all good teams from good leagues," Donovan said. "The 12 is usually a team that is playing with so much confidence in a situation where everyone knows their role. If you're a four-seed and up you're going to have a hard first-round game. It doesn't matter if it's an 11, 12 or 13."

There have been 21 wins by a No. 11 over a No. 6. No. 13 has beaten No. 4 16 times, while No. 14 over No. 3 occurred 13 times since 1985. (A No. 2 seed has only lost to a No. 15 four times, and there has never been a No. 16 over a No. 1).

"I'm not sure why it has been so common, other than the teams are very good," Donovan said. "Sometimes the style of play is hard to go against. ... Butler was a slow team while Creighton was very patient and Manhattan pressed us. I'm not making excuses, but the games are tough."

But does the NCAA Tournament selection committee look at picking potential upsets? Former committee members like Arizona athletic director Jim Livengood say no.

"It's not a punishment to put those high-major teams as a five but some of them aren't playing well," said New Mexico athletic director Rudy Davalos, a former member of the committee. "We'd always scuffle about the first, second, third and fourth seeds, and by the time we got to the fives, there were a lot of teams you could put there."

Davalos said a lot of the No. 12s used to be teams that wouldn't be so today, like Gonzaga was in 2001 when it beat Virginia.

Prior to the brackets being announced Sunday night, Davalos said of his Lobos: "If they stick us at 12, then we would do misery to a five. That would be one of those cases [of a team not getting enough respect]."

There were two No. 12 winners in 2004. Which one are you going with this year?

Andy Katz is a senior writer at ESPN.com.