Stevens will lead the search for a new coach, Charania added.
Per ESPN’s Adrian Wojnarowski, Boston’s front office and coaching staff have been informed of the changes.
Ainge, 62, has served as Celtics president since 2003. He was named NBA Executive of the Year in 2008, the same year the Celtics won their last championship. He had been thinking about leaving his post for several months, Wojnarowski reported.
Stevens, 44, took over as Celtics coach in 2013 after leading Butler University to back-to-back NCAA title game appearances. He was starting to feel burnt out this season, Wojnarowski wrote, leading to his decision to move into the front office.
The Celtics were eliminated from the first-round of the playoffs by the Nets on Monday, losing the series by a 4-1 count after an up-and-down season and 36-36 finish.
Ainge is a franchise legend, being drafted by the team in 1981 out of BYU. He went on to win three championships as a feisty guard with the franchise, playing alongside the likes of Larry Bird, Kevin McHale, Robert Parish and the late Dennis Johnson.
He was eventually traded to the Kings and made Finals appearances as a player with the Trail Blazers and Suns, before retiring in 1995. Ainge was named coach of the Suns in 1996. Early in his NBA career, he also played briefly for MLB’s Toronto Blue Jays.
Ainge resigned from his coaching job in 1999, citing a need for more time with his family. He moved into the Celtics’ front office after briefly serving as an analyst with TNT.
Stevens led the Celtics to a 354-282 record and three appearances in the Eastern Conference finals (2017, ’18, ’20).
The Celtics announced the changes in a press release Wednesday.
“Helping guide this organization has been the thrill of a lifetime, and having worked side-by-side with him since he’s been here, I know we couldn’t be in better hands than with Brad guiding the team going forward,” Ainge said in a statement. “I’m grateful to ownership, all of my Celtics colleagues, and the best fans in basketball for being part of the journey.”
Added Stevens, “I’m grateful to ownership and to Danny for trusting me with this opportunity,” said Stevens. “I’m excited to tackle this new role, starting with a wide ranging and comprehensive search for our next head coach. I love the Celtics, and know the great honor and responsibility that comes with this job. I will give it everything I have to help us be in position to consistently compete for championships.”