Teams on Upset Alert on Day 6 of 2018 NCAA Tournament

The first round of the 2018 NCAA men's tournament featured six major upsets. One was history-making (No. 16 Maryland-Baltimore County's win over No. 1 Virginia), and the others were almost as exciting.

On Sunday, some of those would-be Cinderellas face another round of stiff competition, but thanks to some injuries and some unexpected performances over the past three days, there are more obvious potential upsets going into the second round than there were going into the first.

With the matchup between No. 4 Auburn and No. 5 Clemson excluded because of the even level of competition, here are the possible upsets to keep an eye on in Sunday's slate of games.

Kansas State

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No. 9 Kansas State (-12) vs. No. 16 Baltimore-Maryland County (South Regional)

After making NCAA men's tournament history by becoming the first No. 16 seed to upset a No. 1 seed in the first round, UMBC will look to keep its unprecedented run going against the Wildcats.

There's reason to believe the Retrievers could do it. For one, they didn't pull out a fluke win against top-seeded Virginia—they blew the Cavaliers out by 20 points, proving they can play with anyone. And Kansas State, a No. 9 seed, is not nearly as formidable an opponent as the Cavaliers were.

Kansas State also has health concerns. The Wildcats' leading scorer, junior forward Dean Wade (16.5 points per game), is battling a foot injury and didn't play in their opening-round win over No. 8 Creighton.

"I don't think it's going to be major minutes, but he wants to be a part of it," KSU coach Bruce Weber said regarding Wade's status after Friday's game, per ESPN.com's David Hale.

With the Wildcats short-handed and the Retrievers looking to do something that has never been done in men's college basketball history, this game offers the most intrigue of Sunday's slate.

West Virginia

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No. 5 West Virginia (-12) vs. No. 13 Marshall (East Regional)

West Virginia rolled Friday, defeating No. 12 Murray State handily. Marshall, meanwhile, pulled off a surprising upset against No. 4 Wichita State.

This matchup has a history of bad blood—the in-state rivals played each other every year from 1978 through 2015 until West Virginia backed out abruptly. There will be no shortage of emotion in the building from both sides Sunday, and that may be enough for Marshall to make up for the disparity in talent and steal this one.

On the court, the schools' star point guards—WVU's Jevon Carter and Marshall's Jon Elmore—are the players to watch. Both were outstanding in the first round, helping their teams score 80-plus points. Will this game be another shootout, or will West Virginia's press overwhelm Marshall? Dan D'Antoni's Thundering Herd will be looking to prove their first-round win wasn't a fluke. If Elmore outplays Carter, Marshall will have a great chance to pull another upset.

Michigan State

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No. 3 Michigan State (-9) vs. No. 11 Syracuse (Midwest Regional)

The Orange are riding high after winning the play-in game against Arizona State on Wednesday and upsetting No. 6 TCU on Friday. The Spartans, meanwhile, hung on to beat No. 14 Bucknell by four points in a hard-fought battle.

Syracuse's zone could give Michigan State star Miles Bridges problems, especially with the Orange's size in the frontcourt, featuring 7'2" center Paschal Chukwu along with lengthy wings Oshae Brissett, Marek Dolezaj and Matthew Moyer.

Michigan State has the household names, but in a strategic matchup featuring two Hall of Fame coaches in Jim Boeheim and Tom Izzo, don't overlook a hungry Syracuse team that has scrapped to make it this far.

Purdue

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No. 2 Purdue (-3.5) vs. No. 10 Butler (East Regional)

Purdue lost starting center Isaac Haas to a right elbow fracture in the opening round. The team ruled him out for the rest of the tournament, but according to CBS Sports' Allie LaForce, he practiced with the Boilermakers on Saturday and hasn't closed the door on playing with an elbow brace Sunday.

The Boilermakers wouldn't have needed Haas to blow out No. 15 Cal State Fullerton in the first round. Butler will be much tougher competition after upsetting No. 7 Arkansas. The Bulldogs are led by senior forward Kelan Martin, who had 27 against Arkansas, and sophomore guard Kamar Baldwin, who had 24.

Without Haas in the middle anchoring Purdue's 21st-ranked scoring defense, Butler's lethal wings could overwhelm the Boilermakers and advance to the Sweet 16 for the second consecutive year.

All lines courtesy of OddsShark.