Selection Sunday looms as AP Top 25 teams in major conferences get their final chances to impact where and why they play in the NCAA Tournament.

In the nation’s top leagues, there could be significant swings based on early exits or title runs. Here’s a look at what’s ahead leading up to the biggest day on the sport’s calendar on Sunday:

AAC

The American Athletic Conference Tournament begins Thursday in Fort Worth, Texas, and it gives top-ranked Houston the chance to make a final case potentially for the No. 1 overall seed in the NCAAs.

The Cougars (29-2) are the only team in the country to rank in the top 10 of KenPom’s adjusted efficiency metrics in both offense and defense.

Houston opens against the East Carolina-South Florida winner on Friday, and the tournament is one of five to end on Sunday shortly before the NCAA field is revealed.

ACC

The Atlantic Coast Conference opens its five-day tournament Tuesday in Greensboro, North Carolina. It’s an event lacking a true favorite or team poised to claim a top-tier postseason seed.

Virginia and No. 14 Miami shared the regular-season title, though the Hurricanes are the top seed for the first time since winning the tournament in 2013. But 21st-ranked Duke is the league’s hottest team with six straight wins.

All three open play in Thursday’s quarterfinals, with the Cavaliers on course for a 4-seed, Miami for a 5 and Duke for a 7, according to BracketMatrix.com’s average of 100 mock fields on Monday evening.

BIG 12

Third-ranked Kansas won a national title, overhauled its roster and still finds itself in the chase for the No. 1 overall NCAA seed entering the Big 12 Tournament.

That tournament opens Wednesday in Kansas City, Missouri, with the Jayhawks and other top seeds starting play on Day 2.

Kansas (25-6) has a national-best 15 wins in Quadrant 1 games that top the postseason resume, which had them as the top overall seed in ESPN’s Bracketology projection on Monday evening.

Winning a title this week won’t come easy in a league regarded as the nation’s deepest all year. The field includes No. 7 Texas, No. 10 Baylor, No. 12 Kansas State and No. 22 TCU.

BIG EAST

The Big East opens play Wednesday in New York’s Madison Square Garden with four ranked teams: No. 6 Marquette, No. 11 Connecticut, No. 15 Xavier and No. 24 Creighton.

The top-seeded Golden Eagles, who open play Thursday, have the highest projected NCAA Tournament seed at No. 3 on both ESPN and BracketMatrix, while BracketMatrix has the Huskies and Musketeers as potential 4-seeds.

The Bluejays, who re-entered the poll for a third time this season on Monday, are projected as a No. 6 seed in the NCAAs.

The tournament wraps up Saturday night.

BIG TEN

The Big Ten opens it tournament Wednesday in Chicago with No. 5 Purdue and No. 19 Indiana as the only ranked teams, though the Boilermakers are in the mix for a No. 1 regional seed in the NCAAs.

The Boilermakers are the top seed for Chicago and BracketMatrix listed them as the fourth of the top seeds.

The Boilermakers and Hoosiers both begin play in Friday’s quarterfinals with the title game coming Sunday.

PAC-12

The Pac-12 has two ranked teams in contention for lofty NCAA seeds as the league tournament opens Wednesday in Las Vegas.

Second-ranked UCLA is surging down the stretch and has its highest ranking of the season, putting it in position to contend for a No. 1 regional seed as the top No. 2 seed in BracketMatrix’s projections. Eighth-ranked Arizona is also looking likely for a 2-seed.

The Bruins and Wildcats split their regular-season meetings, with UCLA winning Saturday’s regular-season finale while holding the top seed for Las Vegas. Both teams open play Thursday.

SEC

Fourth-ranked Alabama is the top seed for the Southeastern Conference Tournament beginning Wednesday in Nashville, Tennessee. And the Crimson Tide could be in contention for the top overall NCAA seed with a title run.

Alabama (26-5) owns the top seed in the SEC and opens play in Friday’s quarterfinals, finishing a game ahead of No. 18 Texas A&M in the regular-season race.

The tournament also features No. 17 Tennessee, No. 23 Kentucky and No. 25 Missouri, with the title game set for Sunday.