Withey had 16 points and 16 rebounds, and Releford finished with 22 points for the Jayhawks (31-5), who also knocked former coach Roy Williams’ team out of the NCAA tournament during their 2008 title run and again last season, when Kansas marched to the Final Four.
Kansas will play No. 4 seed Michigan at Cowboys Stadium in Arlington on Friday.
P.J. Hairston scored 15 points and James Michael McAdoo finished with 11 for the Tar Heels (25-11).
Florida 78, Minnesota 64
Mike Rosario scored 25 points and Florida used an overpowering first half to roll past Minnesota and into the Sweet 16 for third consecutive year.
The No. 3 seed Gators (28-7) shot a blistering 65 percent in the first half and led by 21 at halftime. Florida plays No. 15 seed Florida Gulf Coast at Cowboys Stadium in Arlington on Friday.
Andre Hollins scored 25 points to lead the No. 11-seed Gophers (21-13). Hollins’ 3-point shooting sparked a second-half rally that pulled Minnesota within seven points, but Rosario’s sixth 3-pointer with 3 minutes left pushed the Gators’ lead back to 16.
Rosario was 8 of 12 shooting overall and 6 of 9 on 3-pointers.
Florida Gulf Coast 81, San Diego State 71
Florida Gulf Coast became the first 15th seed to advance to the Sweet 16 with a convincing win over seventh-seeded San Diego State just two days after an upset of second-seeded Georgetown.
The Eagles advanced to play Florida in Arlington, Texas, on Friday.
Point guard Brett Comer finished with 10 points and 14 assists, while Bernard Thompson led the team with 23 points.
Florida Gulf Coast trailed at the halftime for the first time in 22 games when San Diego State held a 35-34 lead. But a 17-0 run in the second half turned an early 54-52 lead into a 71-52 edge for the Cinderella story.
La Salle 76, Ole Miss 74
The last time La Salle advanced this far in the NCAA tournament the field was only 24 teams.
Tyrone Garland banked a scooping layup with 2 seconds left and 13th-seeded La Salle beat No. 12 seed Mississippi, vaulting the Explorers to their deepest run in the NCAA tournament since they played for the 1955 championship.