The term "X-factor" is tough to define. In a single-elimination tournament, everyone who plays meaningful minutes is an X-factor to an extent. A player can be an X-factor for different reasons, too. Maybe he's the offensive spark plug or the defensive stopper. Maybe he's the glue guy whose modest stats belie his massive impact. Maybe he's the versatile player who can fit any lineup.

Perhaps an X-factor is best defined as the player who most raises both his team's ceiling and floor: not a star, but the player who can take his team to a new level when stars are playing well and keep his team afloat when stars are struggling.

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Thirty of the last 32 champions have been top-three seeds, so we'll start there.

No. 1 seeds

Gonzaga: Andrew Nembhard

Gonzaga has made the championship game twice, and both times, it had outstanding guards. In 2017, it was Nigel Williams-Goss. Last year it was Nembhard and Jalen Suggs. For the 'Zags to make it over the hump this year, it's up to Nembhard alone.

Nembhard logged 40 minutes in each of the last three games. He is not only the main facilitator that makes Gonzaga's offensive machine go but also a key shot creator. His 37 made 2-point jumpers were second on the team behind Drew Timme. His splits in wins versus losses tell you all you need to know:

  • In 26 wins: 12.1 PPG, 48% FG pct, 39% 3-pt FG pct, 1.5 TOPG
  • In three losses: 8.3 PPG, 31% FG pct, 10% 3-pt FG pct, 3.7 TOPG

Arizona: Dalen Terry

In case you needed another reminder of Terry's multifaceted skill set, he racked up 27 points, 11 rebounds, 10 assists and just two turnovers across the Pac-12 Tournament semifinal and final, doing an admirable job helping fill in for injured starting point guard Kerr Kriisa.

Kriisa's status is up in the air, but even if he does return, Terry is an indispensable part of the Wildcats. He can play four positions, he's the team's best perimeter defender, and he does the little things that, put together, play a big part in Arizona's success. The more often you hear Terry's name on the game broadcast, the better.

Kansas: Jalen Wilson

I went back and forth here between Wilson and Christian Braun, both of whom are very good players who fill several roles and will have to play well for Kansas to win it all. Wilson is a terrific defender -- his 95.7 defensive efficiency is second-best on the Jayhawks -- and he gobbles up defensive rebounds at a team-best 21.4% rate.

On offense, Wilson gets to the free throw line at a higher rate than any Kansas player outside center David McCormack. Wilson also averages more points against ranked teams (12.3) than he does against unranked teams (10.3) this season.

Baylor: Jeremy Sochan

What do we make of the defending champs? Leading scorer LJ Cryer hasn't played since Feb. 16, though he could return. Jonathan Tchamwa Tchatchoua was lost for the season four days prior. Yet the Bears have managed to stick together, and Sochan is a significant reason why.

One game that sticks out in Sochan's X-factor status is a 17-point, five-rebound performance in a Feb. 26 win over Kansas. A good finisher at the rim with solid touch in the midrange, Sochan is emerging as Scott Drew's most-used big man.

No. 2 seeds

Duke: AJ Griffin

There's no doubting Griffin's skill. At his best, the 6-foot-6 freshman is a 3-point marksman who can also finish at the rim and create his own shot when needed -- all reasons he's seventh in Kyle Boone's NBA Draft prospect rankings. But no one defines "the team is good when he's good; the team is bad when he's bad" as much as Griffin:

  • In 28 wins: 11.4 PPG, 53% FG pct, 50% 3-pt FG pct
  • In six losses: 5.8 PPG, 36% FG pct, 27% 3-pt FG pct

The fact that a potential top-10 pick is considered an X factor shows how talented Duke is. Still, Griffin disappears in too many games, and his inconsistency has been a bellwether of Duke's inconsistency as a whole.

Villanova: Jermaine Samuels

Calling Samuels a "glue guy" is a disservice to just how good he is. This season, he had three double-doubles, all in wins over ranked teams (Tennessee, Seton Hall and UConn). His most recent -- a 21-point, 12-rebound effort against the Huskies in the Big East semifinal -- was the crown jewel.

A terrific, versatile defender with a team-best 97.7 defensive rating, Samuels plays both power forward and center for a thin Villanova frontcourt. He also has championship experience as a freshman on the 2017-18 title team.

Auburn: Wendell Green Jr.

Auburn has a potential No. 1 overall pick in Jabari Smith and one of the nation's best big men in Walker Kessler, but their most-used player on the offensive end is their mercurial point guard, Green Jr. An Eastern Kentucky transfer, Green Jr. isn't afraid to shoot from anywhere in any situation, but that hero ball approach has been up-and-down.

Since Feb. 1, Green has shot 34%, the second-worst number of any SEC player who has attempted at least 10 shots per game over that stretch, only ahead of his backcourt mate, K.D. Johnson. Guard play is crucial in the NCAA Tournament, and Green Jr. will have to balance his fearless nature with more composed play.

Kentucky: Kellan Grady

On Feb. 23, Grady nailed seven 3-pointers in Kentucky's win over Alabama. At that point, he was shooting over 45% from deep. Since then, he's at 21.7%.

Kentucky has one of the nation's best offenses despite taking a 3-pointer on just 28% of its possessions this season, 350th in Division I. When the Wildcats do shoot from deep, it's usually by Grady. At some point, they'll need those shots to go in. Grady is shooting 34% from 3-point range in losses this year compared to 45% from 3-point range in wins.

No. 3 seeds

Texas Tech: Terrence Shannon Jr.

It's been an up-and-down year for Shannon Jr., who has dealt with back and knee injuries, but he provides a level of guard scoring no other Texas Tech player can. Take a mid-February two-game stretch in which Shannon Jr. totaled 34 points (on 57% shooting) and seven assists in wins over TCU and Baylor.

A very good finisher at the rim (70% this season), the 6-6 lefty can play point guard, shooting guard or small forward, and, along with Bryson Williams, will be a primary option late in games.

Tennessee: Josiah-Jordan James

The Volunteers have a deep backcourt and a long list of big men, but on the wing, it's pretty much James, and James alone. He'll play small forward when the Vols go big and power forward when they go small, but mostly he'll just play; he's been in each of Tennessee's four most-used lineups over the last five games.

James caught fire beyond the arc in March, making 52% of his 3-pointers this month compared to just 29% prior. It's no coincidence Tennessee is 5-0 this month. He also led the team in steals and blocks this season.

Wisconsin: Tyler Wahl

Wahl is an enjoyable player to watch. He's not overpowering or super athletic, but he's crafty in the post and can face up. He shot nearly 52% on 2-point jumpers this season, by far the best number on the Badgers. For reference, Johnny Davis shot under 36% on those shots. Wahl has improved in every major statistical area every year, and he's an underrated defender. Davis will rightfully get the headlines, and Brad Davison will hit a big shot or two, but Wahl (nine games of 15+ points this season) will be a key in the Badgers' potential Tournament run.

Purdue: Trevion Williams

The Big Ten Sixth Man of the Year, Williams is one of the most skilled passers you'll see, regardless of position. That he does it at 6-10 and 255 pounds makes him all the more impressive. Williams' 6.2 assists per 40 minutes this season are the most by any player 6-10 or taller in the last quarter century.

While 7-4 Zach Edey starts ahead of him, Williams is a huge part of Purdue's outstanding offense. The Boilermakers can play through him in the post, even with star guard Jaden Ivey on the court. Williams is also a strong defender (team-best 94.0 defensive rating) and rebounder. Williams likely won't start games, but expect him to finish them.