The opening weekend of the 2015 NCAA tournament brought plenty of upsets, but the Sweet 16 is filled with familiar names and powerhouses ready to make a run at the championship.Top-seeded Villanova and No. 2 Virginia are already out of the running in the East Region, but it says a lot that the only double-digit seed in the final 16 is No. 11 UCLAone of the winningest programs in college basketball.With most of the national championship contenders still very much alive heading into the second weekend of the Big Dance, the final 15 games promise to deliver.Here's an early look at all of the matchups.BracketSchedule Top Matchup to Watch: No. 2 Arizona vs. No. 6 XavierA shocking early upset couldn't keep the bottom half of the West region from producing a mouth-watering matchup.No. 3 Baylor may have been upset by a 14th-seeded Cinderella in Georgia State on the tournament's opening day, but No. 6 Xavier put an end to the Panthers' season on a remarkably hot shooting performance.Meanwhile, No. 2 Arizona won each of its opening two contests in Portland, Oregon by 15 or more points to breeze into the Sweet 16.So the matchup is on between the Musketeers and Wildcats, and its underlying storyline is a juicy one, as noted by Fox Sports:It's apparent that Thursday's game will be a tough one for both head coaches, who worked together at Xavier before Chris Mack eventually took over for Sean Miller following Miller's exit to Arizona. But that happened way back in 2009, so Mack doesn't see it as a distraction for anyone other than the two individuals in question.It's hard to play against one of your best friends in the business," Mack told reporters."But it really won't matter to our guys, nor will it matter to Arizona, because they don't know me from a bucket of paint."If there's one thing that is certain, though, it's that Xavier's program hasn't seen much of a fall-off amid that transition. The Musketeers have made it this far so many times that CBS Sports' Seth Davis had to correct his tweet:This season has brought its fair share of struggles for Xavier in Big East play, going just 9-9 and losing nonconference games to Long Beach State and Auburn.But with big center Matt Stainbrook dominating the post along with Trevon Bluiett and Myles Davis having spectacular tournaments, the Musketeers are becoming awfully tough to beat.With that said, it's no secret that these two teams are on different planesat least right now.Getting to the Sweet 16 is no small task, but Xavier only had to go through 11th-seeded Ole Miss and 14th-seeded Georgia State to get here. Without shooting 81 percent in the second half against Georgia State, it wouldn't even be here.As for Arizona, it answered an early gut punch from underrated No. 10 Ohio State in the third round and played nearly perfect basketball with only two second-half turnovers against the Buckeyes.The Wildcats are simply too talented to be held down for 40 minutes against an inferior team, which has a bit to do with Miller's incredible record as the favorite, per ESPN Stats and Info:This isn't one of the better teams that Xavier has brought into the Sweet 16, and Miller just so happens to boast the most championship-ready roster he has had in Tucson on the other side of the matchup.Xavier's guard play has held up well in the opening weekend, but Rondae Hollis-Jefferson is guaranteed to shut down option No. 1 and T.J. McConnell's recent tear has been a sight to see.There aren't many teams on this half of the tournament bracket capable of beating Arizona, and Xavier isn't one of them.The Wildcats will flex their defensive muscle and cruise into the Elite Eight.Prediction: Arizona 64, Xavier 54 Click here to read full news..