Key trait: Like Virginia and an ever-widening host of teams across the country, Arizona also plays a pack-line man-to-man defense. But it's safe to say no team has ever put so much athletic talent -- or used it so well -- in the service of pack-line principles. The Wildcats are the nation's best defense on a per-possession basis. They have been pretty much all season. It is what makes them such a daunting task for any team in the bracket, and especially San Diego State. You might match up athletically with Arizona. You might get a few stops. But how do you score on Sean Miller's team?
How they got here: This was supposed to be a quiet year in Viejas Arena. San Diego State was supposed to rebuild. Instead, Steve Fisher recovered from a series of offseason losses (Jamaal Franklin to the NBA, Chase Tapley and others to graduation) and, from who remained, assembled what might be the best defensive team of his career. Meanwhile, longtime role player Xavier Thames morphed into a scoring force with the ball in his hands. The result? A 31-4 record and another Mountain West title. So much for rebuilding.
Key trait: San Diego State is not a difficult team to figure out. On offense, the Aztecs give Thames the ball, send approximately 7,000 ball screens per game at his defenders and let him go to work. On defense, they play good, hard, fundamental man-to-man. Knowing these things doesn't make it any easier to solve, though, because both Thames and (especially) that defense are so very good at setting the terms of the engagement. But if you can somehow take Thames out of the game, San Diego State can't score. Arizona looks well-suited to do exactly that.
How they got here: True story: As of Feb. 8, Baylor was 2-8 in Big 12 play. But then point guard Kenny Chery finally got fully healthy, and center Isaiah Austin started to genuinely embrace his role on the interior, and all of a sudden the Bears rattled off 11 wins leading up to Sunday's absolute demolition of Creighton and star forward Doug McDermott.
Key trait: What makes Baylor suddenly so tough was readily apparent against the Bluejays and college basketball's No. 5 all-time leading scorer Sunday night. It can be summed up in one word: length. Baylor has a nice combination of heady guard play from Chery and sharpshooter Brady Heslip on the perimeter and tons of size in Austin (a 7-footer with a crazy wingspan) and Cory Jefferson. For most of the season, Baylor used that length better on the offensive end, where it was one of the nation's best second-chance teams. Now, Scott Drew is using that size to frustrate opponents with an adaptive, reactive 1-3-1 zone. Can Wisconsin shoot over it?
How they got here: Wisconsin has been one of the best teams in the country for all but two weeks of the season. Those two weeks came in late January, when a team that had beaten Florida, Saint Louis and Virginia suddenly lost five of six, including losses to Indiana, Minnesota and (weirdest of all) at home to Northwestern. Other than that, Bo Ryan's team has been a top-end version of the teams he always produces: smart, versatile, efficient and experienced. Saturday's third-round win over a really hot Oregon team, in front of a raucous Milwaukee crowd, was an awfully good primer.