We're down to four, and while this tournament definitely had some Cinderella stories, we're left with four powerhouses -- Kansas, Duke, Villanova and North Carolina

Those region winners will battle it out for the National Championship, and the semifinals of the Final Four get going on Saturday night, with a top-shelf matchup between 1 seed Kansas and 2 seed Villanova followed by UNC and Duke squaring off in a historic rivalry showdown.

Which player could be the X-Factor for each squad?

Brandon Slater, Villanova

How will Villanova handle the absence of Justin Moore, who suffered a season-ending Achilles injury in the Elite Eight win over Houston? That's the big question for the Wildcats as they gear up to take on Kansas.

Moore was a key piece who averaged 14.8 points and 4.8 boards, so his shoes won't be easy to fill. Caleb Daniels, the fourth-leading scorer on 'Nova at 10.2 points per night, will likely step into the starting five in Moore's place. That will thin out the Wildcats' bench and probably lead to Chris Arcidiacono and Bryane Antoine seeing an increased role.

But I think it's Brandon Slater who could be a vital cog on Saturday.

Slater has started all 37 games for Villanova this season, and he's usually an afterthought on offense, holding a mere 14.5% usage rate for the year, according to Sports-Reference. He's played at least 20 minutes in all four NCAA Tournament games but has netted just five total points in the Big Dance and hasn't made a field goal since the first round.

Slater won't become an offensive force all of the sudden, but Moore's absence could lead to a couple more looks. Arcidiacono and Antoine played a combined two minutes versus Houston, so Villanova coach Jay Wright may elect to ride his starting five as much as he can versus the Jayhawks.

That would mean the Wildcats will likely need a little more offensive juice than usual from Slater, who has shown decent scoring ability at times this season, including a February stretch in which he reached double-digit points in seven straight games. A good scoring night from Slater could help Villanova -- who is a 4.5-point underdog, per NCAAB odds -- advance to the title game.

Remy Martin, Kansas

When Remy Martin fills it up, the Jayhawks usually win.

Martin, a transfer from Arizona State, has had an up-and-down season for Kansas, but he's been playing pretty dang well of late.

In four NCAA Tournament games, Martin is averaging 16.8 points, 5.3 boards, 3.3 assists and just 1.3 turnovers per game while shooting 54.5% from the floor and 41.7% from three. Those numbers are better across the board than his averages for the season, which stand at 8.6 points, 3.0 rebounds, 2.6 assists and 1.4 turnovers per night on 46.5 shooting overall and 35.8% from three.

Martin is playing his best ball at the right time. That's great news for KU because when Martin is scoring well, the Jayhawks rarely lose. Martin has suited up for five of Kansas' seven defeats this season, and he's scored more than five points in just one of those losses.

Martin and Mitch Lightfoot give Kansas two solid options off the bench, and with Moore's injury thinning out Villanova's rotation, depth is one place where Kansas should have a clear advantage on Saturday. If Martin keeps playing like he has so far in the Big Dance, the Jayhawks will be a tough out.

Our algorithm gives Kansas a 60.3% chance to beat 'Nova.

A.J. Griffin, Duke

Duke and UNC played twice this year and split the meetings, with each winning by double-figures on the other's home court.

When Duke won by 20 in Chapel Hill, A.J. Griffin finished with 27 points on 11-of-17 shooting, including 8 for 11 on two-pointers, in what was maybe his best game of the season. In the 13-point home loss to the Tar Heels, Griffin had five points on a 2-of-5 effort from the field in 34 minutes.

Obviously, a lot more than Griffin's performance decided those two games, but Griffin -- a freshman who was a top-20 recruit and will be a likely top-10 pick this summer -- has the talent to be a decisive force for the Blue Devils when he's in top form. He just hasn't been in top form all that much.

Griffin has scored 11 or fewer points in six of his last eight games, and he was averaging just 9.3 points through the first three rounds of the tourney before he went off for 18 points on 7-for-9 shooting against Arkansas in the Elite Eight.

Griffin being on his game would go a long way toward helping the Blue Devils knock off North Carolina, but even if he's not scoring, Griffin will be needed on the boards versus a UNC squad that is averaging 13.5 offensive rebounds per game in the NCAA Tournament, the most among Final Four participants.

According to our model, Duke has win odds of 66.4% against UNC.

R.J. Davis, North Carolina

Across UNC's last nine games, R.J. Davis' points tally has been all over the place.

In that span, he has three games of 17-plus points, including a 30-point masterpiece versus top-seeded Baylor in the second round, but he has also produced single-digit points four times in that stretch. His Big-Dance point totals are 4, 30, 12 and 9.

Scoring isn't always the main priority for Davis with UNC having Armando Bacot, Brady Manek and Caleb Love at its disposal, but when Davis is putting the ball through the hoop, this Tar Heels squad becomes really tough to defend.

Davis' volatility played out in the two regular-season matchups against Duke. In the home loss to Duke, Davis struggled en route to 11 points. In the win at Cameron, Davis totaled 21 points.

The Tar Heels are 4.0-point 'dogs, and if they're going to topple the Blue Devils, Davis likely needs to find his scoring touch, especially from the outside.