Oklahoma City announced the move Tuesday night. The Thunder posted a 44-28 regular season record in 2019-2020 before they lost to the Houston Rockets in the first round of the NBA playoffs in Orlando, Fla.
"Coaching the Oklahoma City Thunder the past five seasons has been a great honor, and I thank [Thunder owner] Clay Bennett, general manager Sam Presti and the entire organization for the opportunity," Donovan said in a news release.
"I have a great respect and admiration for the players I coached in Oklahoma, and I also want to thank the coaches I worked with, who gave unbelievable time and expertise to our common goal.
"Lastly, I want to thank the Oklahoma City community for being so welcoming to my family during our time here. This place will always be special to us. I will always hold this organization in the highest regard and wish the Thunder and their fans the success they deserve."
Donovan posted a 243-157 record during his tenure with the Thunder. He had an 18-23 mark in the playoffs. The Thunder wnet 55-27 in Donovan's first season. He was hired on April 30, 2015, after he spent 19 years as coach of the Florida Gators. His contract with the Thunder expired after the 2019-2020 season.
"I have great respect for Billy and will always appreciate our work together. He is a terrific basketball coach and we are proud of what he has accomplished with the Thunder," Presti said. "We had planned to sit down at the end of the season and discuss the best way to move forward for both of us.
"After those discussions, it became apparent that we couldn't provide him the information on the future direction of the team over the next several seasons to give him the level of clarity that he understandably desires at this stage of his career. Therefore, we close this chapter and reflect fondly on all that he has given to the team, organization and community. Billy will always have a place in the Thunder family."
Donovan is likely a candidate for several job openings in the NBA after coaches were fired after the season. The New Orleans Pelicans, Indiana Pacers and Philadelphia 76ers are among the teams without a coach.