North Carolina basketball coach Roy Williams is retiring, the university announced Thursday morning. The legendary college basketball figure is stepping down after one of the greatest careers in the history of the sport.

Williams ranks third all-time among men’s Division 1 coaches with 903 wins. The 70-year-old spent 18 years at North Carolina after serving as the coach of Kansas for 15 seasons. He won three NCAA championships with the Tar Heels.

Williams is set to address the media at a 4 p.m. ET press conference.

There is plenty of speculation about why Williams chose now to retire. He has been frustrated with the direction of college basketball, according to Stadium’s Jeff Goodman, including the number of recent transfers.

North Carolina was defeated by Wisconsin in the first round of the 2021 NCAA Tournament. A No. 8 seed with an 18-11 record, the Tar Heels had one of their worst seasons under Williams.

The opinion that the 2021 season was a "failure" may be viewed as a testament to Williams’ success with the program. Before Williams was hired in 2003, North Carolina missed the NCAA Tournament two straight years for the first time in nearly four decades.

Williams led the Tar Heels to 16 NCAA Tournament appearances and five Final Fours. Kansas made four Final Four appearances with two losses in the national championship when Williams was the coach.

There was no immediate word on a possible replacement but early favorites include Williams' longtime assistant Hubert Davis and Baylor coach Scott Drew.

roy williams unc 2016
Head coach Roy Williams, center, and the North Carolina Tar Heels celebrating after winning the 2016 Atlantic Coast Conference championship game. Getty Images