Four down. Four to go. And Day 1 of the Sweet 16 ended with some drama.

Xavier, the lone double-digit seed to make the Sweet 16, kept its run in the NCAA tournament alive with a 73-71 upset of No. 2 seed Arizona. The Musketeers ended the game on a 9-0 run to advance to their third Elite Eight in program history and first since 2008. This came after Oregon ended Michigan's magic run, Gonzaga squeaked past valiant West Virginia, Kansas absolutely crushed Purdue.

Those four winners meet Saturday (Oregon plays Kansas and Gonzaga squares off against Xavier) to see who goes to next weekend's Final Four in Phoenix.

Before that, though, we have to figure out the other half of the Elite Eight. You didn't make any plans for tonight, did you?

Thursday's box scores, recaps, play-by-plays and video highlights

South, East Regionals tonight

• 7:09 p.m. ET — (4) Butler vs. (1) North Carolina (CBS) WATCH LIVE
• 7:29 p.m. ET — (7) South Carolina vs. (3) Baylor (TBS) WATCH LIVE
• 9:39 p.m. ET — (3) UCLA vs. (2) Kentucky (CBS) WATCH LIVE
• 9:59 p.m. ET — (8) Wisconsin vs. (4) Florida (TBS) WATCH LIVE

What to look for in tonight's Sweet 16

• North Carolina vs. Butler: The Bulldogs of Butler are the non-bluebloods of the South region in Memphis (see below). To get past the tournament's top seed, they'll need to control steady Tar Heels' point guard Joel Berry. And the man who gets that job is Kamar Baldwin, who has been a relentless reason that Butler has made it this far in the tournament. 

• South Carolina vs. Baylor: This one may turn on how well Baylor, a team that turns the ball over a lot, performs against the Gamecocks' defense, which is used to turning over other teams. A lot. Baylor point guard Manu Lecomte will have a lot of pressure on his shoulders in the game at Madison Square Garden in New York. And on his hands and arms and legs and head, too, from that relentless South Carolina D.

• UCLA vs. Kentucky: The marquee matchup of the night -- the weekend? the tournament? the season? -- showcases two teams with 19 national titles between them. Not to mention De'Aaron Fox, Kentucky's fantastically athletic point guard, against Lonzo Ball, UCLA's slick floor general. These two teams played in December at UK's Rupp Arena and UCLA won going away. This is different, though. For everybody.

• Wisconsin vs. Florida: Without rim protector John Egbunu, the Gators may have a hard time against Wisconsin, a team that revels in banging around in the paint. The Gators haven't missed their shot-blocker terribly so far, with wins over East Tennessee and offensively-challenged Virginia. But Wisconsin's big and talented front line will offer a different test altogether. More like a 400-level physics final.

NCAA.com's Joe Boozell delves further into what makes the second half of this Sweet 16 so sweet.

Good things come in threes (and Fours)

With Kentucky, North Carolina and UCLA, the South is hands down the bluest-blooded region in college basketball this weekend. Those three teams (Butler, no slacker itself, is the fourth in Memphis) account for almost 31 percent of all college hoops championships, and at least one of those three has appeared in more than 56 percent of all Final Fours, including 10 of the last 12.

None of that haughty history guarantees a trip to the Final Four this year. It does guarantee, though, some basketball worth watching tonight. NCAA.com's Mike Lopresti points out three things -- OK, it's a lot more than three -- about the South's terrific trio.

How did we get here?

March has flown by, hasn't it? It seems like just last week all our brackets were so pristine.

Wait a minute. It was just last week.

Anyway, if you've missed any of the tournament, we have you covered, with video highlights, box scores, recaps and play-by-plays of every game of March Madness. Just click on the game you want to re-live on our interactive bracket.

Nostalgic? You can re-live last year's tournament, too.

View the updated bracket | Check your bracket

Mark your calendar

Sweet 16 concludes: Tonight!
Elite Eight begins: Saturday
Final Four in Phoenix: Semifinals on Saturday, April 1; Championship game on Monday, April 3

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