Who's No. 1?

The final answer of the NCAA Tournament is still a March mystery.

But in the Elite Eight, the answer is much more translucent — each region is represented by the No. 1 seed for the first time since 2009.

The underdogs stole the spotlight early in the tourney. This weekend, make way for the top dogs.

North Carolina, Virginia, Kansas and Oregon have all flexed their collective top-seeded muscle with dominant victories that not only flaunted their superiority so far, but showed an all-No. 1 Final Four is a legitimate possibility in Texas.

The most intriguing roadblocks come Saturday in a pair of 1-2 matchups.

Oklahoma (28-7) takes on No. 1 Oregon (31-6) in the West Regional.

KU (33-4) plays No. 2 Villanova (32-5) in the South Regional.

"Both of us are playing our best basketball right now, and both of us have played pretty well during the season," Villanova coach Jay Wright said. "It's one-seed, two-seed and teams that I think feel very good about how they're playing. So I would say that's a heavyweight matchup."

Much like in the jumbled alphabet soup of boxing organizations, there are quite a few heavyweight contenders left on Sunday.

Virginia (29-7) plays No. 10 Syracuse (22-13) in the Midwest Regional final.

The top-seeded Tar Heels stomped Indiana on Friday night and move on to play sixth-seeded Notre Dame (24-11) in the Elite Eight.

"The Irish don't lose on Good Friday or Easter Sunday," Notre Dame coach Mike Brey told his team in the locker room after beating Wisconsin. "Can I get an Amen!"

Notre Dame might need a few amens and a handful of Hail Marys on Sunday — Notre Dame's 31-point loss to UNC in the ACC tournament on March 11 was the worst ever for the Irish under Brey.

No wonder the tourney is dubbed March Madness. The NCAA Tournament has only once sent all four No. 1 seeds to the Final Four, in 2008 when Kansas, Memphis, North Carolina, UCLA advanced and the Jayhawks topped the Tigers for the national championship.

Four No. 1 seeds have reached the Elite Eight seven times since seeding began in 1979, according to STATS LLC.

— 1987; Georgetown, Indiana, North Carolina, UNLV.

— 1993; Indiana, Kentucky, Michigan, North Carolina.

— 2001; Duke, Illinois, Michigan State, Stanford.

— 2003; Arizona, Kentucky, Oklahoma, Texas.

— 2007; Florida, Kansas, North Carolina, Ohio State.

— 2008; Kansas, Memphis, North Carolina, UCLA.

— 2009; Connecticut, Louisville, North Carolina, Pittsburgh.

With the Tar Heels, Cavaliers, Jayhawks and Ducks joining the list this season, it's truly the Elite "Eighth" time the 1s are still on the line.

The Wildcats have won three tournament games by an average of 24 points, including a 23-point win over No. 3 Miami in the Sweet 16. Villanova is shooting nearly 60 percent from the field in the tournament.

"They're on fire right now," said Kansas coach Bill Self, who noted his Jayhawks have been just as dominant.

Oregon might be the No. 1 seed most susceptible to a loss, though both the Ducks and the Sooners rely on deep, balanced rosters of athletic players surrounding an elite scorer: Oklahoma's Buddy Hield and Oregon's Dillon Brooks.

The Sooners' core four of Hield, Ryan Spangler, Jordan Woodard and Isaiah Cousins will start its 104th consecutive game together, along with 36 straight starts by Khadeem Lattin. OU is after its first Final Four trip since 2002.

"We ride and fight all together, so I think ending on a good note would be special for us," Hield said.

Even before the ball is tipped April 4 in Houston for the national championship, the true No. 1 is already stamped ACC. North Carolina and Notre Dame will determine one of two guaranteed Atlantic Coast Conference spots in the Final Four. The Fighting Irish beat Wisconsin 61-56 on Friday.

It will be the same case in the Midwest Regional, where the Virginia-Syracuse matchup ensures at least half the Final Four will be from the ACC. The conference will also have a team play for the national title.

"That's good, but at the end of the day, I'm a Carolina basketball player so as long as we're advancing and we're that No. 1 seed that keeps on moving, that's all I care about," North Carolina guard Joel Berry III said