The two top seeds in action Sunday could have tough tests. There is a marquee matchup with Kansas and Syracuse, plus Cinderella stories Gonzaga and Indiana State battling.

Here are Sunday's matchups by region (seeds in parentheses):

MIDWEST
Illinois (1) vs. Charlotte (9)
Bill Self's team will have a challenge against a Charlotte club that is on a roll. The 49ers have one of the premier diaper dandies in Rodney White. Charlotte showed great balance in its attack in the win over Tennessee.

The Illini need a strong showing from Brian Cook up front. Cook had a solid game against Northwestern State in the first round, scoring 15 points. Cory Bradford has to keep hitting the trifecta; he had four in the first round.

Kansas (4) vs. Syracuse (5)
What a matchup on the sidelines as Roy Williams and Jim Boeheim square off. Boeheim just got his 600th win when the Orangemen beat Hawaii.

Preston Shumpert wasn't bothered by an eye injury, scoring 18 points against Riley Wallace's squad. Boeheim's starters logged a lot of minutes in the first round, and it will be tested against a deeper Kansas team.

The key could be the Jayhawks' front line. Nick Collison, Drew Gooden and Kenny Gregory dominated against a good, underrated Cal State-Northridge team. The trio combined to hit 27 of 37 shots from the floor. Syracuse could have problems on the boards against the physically talented Jayhawks.

Mississippi (3) vs. Notre Dame (6)
The Irish came out strong in their win over Xavier. Troy Murphy and Ryan Humphrey came through in the second half, and the perimeter shooting of David Graves and Ryan Carroll, who combined to go 9-for-9 from the field in the first half, stood out.

The Rebels had a Maalox Masher against Iona. The Gaels had a chance to win but lost the ball in the last-second scramble. Mississippi has a number of different scoring threats, and Emanuel Wade came out of nowhere to key the win over Iona. Wade, who averaged four points a game, had 19 big ones.

Mississippi's quickness could give Notre Dame some trouble, though I feel the Irish, with Murphy and Humphrey, are in good shape in this matchup.

Arizona (2) vs. Butler (10)
Butler will not be intimidated. These teams met earlier this season in Tucson. The Bulldogs were down 62-60 with less than six minutes left before the Wildcats pulled away to win, 72-60. Loren Woods had a big game in the win,and he has been more aggressive lately. Woods and Michael Wright were too much up front for Eastern Illinois.

Gilbert Arenas was 1-for-9 shooting in the first meeting against Butler. Arenas won't have that kind of performance again. No way. He has been playing as well as anyone.

Butler certainly put a hurt on the ACC and Wake Forest, jumping to a 43-10 halftime lead. I was impressed that they had just one turnover in the first half. Thad Matta's team can play solid defense, and LaVall Jordan can flat-out play.

This will not be an easy game for Lute Olson's squad.

SOUTH
Michigan State (1) vs. Fresno State (9)
Tom Izzo and Jerry Tarkanian have both cut down the nets before. The Spartans suffered through struggle city in the first round, leading Alabama State by just four points at half.

Izzo must have given a great speech because Michigan State gave up just 10 points in the second half. Andre Hutson was strong up front as the Spartans pulled away.

One concern is the play of Charlie Bell. He has to get hot shooting the trifecta, breaking out of the slump.

Fresno State has been boosted by great play of Demetrius Porter, who had 27 points against California. Tark needs Tito Maddox to come through distributing the rock, while Chris Jefferies on the baseline must play up to par. Melvin Ely could be a force in the middle. This is a tough second-round showdown for the defending champions.

Gonzaga (12) vs. Indiana State (13)
Wow, it was shock city as Virginia and Oklahoma both went down. Royce Waltman's team got a great performance from Matt Renn.

Gonzaga is not a Cinderella any more. Dan Dickau is one of the best unsung players in America, coming up with 29 points against Virginia. Casey Calvary is a veteran of these NCAA tournament runs, and he makes big play after big play.

Florida (3) vs. Temple (11)
Can Florida shoot well against Temple's zone? Billy Donovan's team needs Brett Nelson and Teddy Dupay to hit the three. Lynn Greer had a Bo Derek, a perfect 10-for-10, from the foul line against Texas. Greer is one of the most underrated guards in America. Greer and Quincy Wadley could give the Gators trouble.

Udonis Haslem, who starred against Western Kentucky and 7-foot-1 center Chris Marcus, could have problems as the Owls pack in the zone. Haslem against Kevin Lyde is a matchup to watch.

This is not an easy draw for Donovan, who has done a super job despite a number of injuries. Florida misses Brett Wright and Justin Hamilton, who would have added depth to the rotation. Neither Florida nor Temple has the depth it enjoyed going into the season.

North Carolina (2) vs. Penn State (7)
The Tar Heels pounded the ball inside against Princeton as Brendan Haywood and Julius Peppers were too much for the Tigers. Joseph Forte is still struggling with his shot, though he had a double-double with 13 points and 12 rebounds.

Penn State has more than just the Crispins, Joe and Jon. Titus Ivory and Gyasi Cline-Heard, the son of former NBA'er Garfield Heard, are unsung heroes.

Jerry Dunn's team has big wins over Illinois, Michigan State and Kentucky. The size of the Tar Heels will give the Nittany Lions problems.