Coach Rick Pitino's Cardinals started off 16-1 and climbed to No. 4 but were hampered by injuries and finished the regular season by dropping eight of their last 12.
February road losses to Cal and Oregon State put the Wildcats precariously close to bubble.
Red Raiders struggled through a 5-7 stretch at the end of the regular season before losing to Oklahoma State in the Big 12 tournament.
The Friars have impressive wins over Illinois and UConn, but they have stumbled down the stretch and enter the tournament having lost three straight.
The Gamecocks climbed into the Top 25 at No. 24 in late January but have won only four of their last 11 games.
The Wildcats have been reeling since junior forward Isaiah Fox went down with a knee injury on Nov. 28. Seventh man Ivan Radenovic, a freshman forward, has averaged just nine minutes in the last four games.
Injuries or foul trouble could doom the Blue Devils, who go only seven deep. Eighth man Nick Horvath, a senior forward, is averaging just 6.5 minutes per game.
Leading scorer Gerald Fitch, a senior has often come off the bench over the last weeks to help spark a six-man rotation. Foul could doom this team.