"A decision about his future with the Celtics beyond this season will be made at a later date," the Celtics said in a statement. "The suspension takes effect immediately."
Udoka had an consensual relationship with a female Celtics staffer, a person familiar with the situation told USA TODAY Sports. The person requested anonymity because they were not authorized to speak about the sensitive nature of the topic.
Assistant coach Joe Mazzulla will serve as interim coach, according to ESPN.
"I want to apologize to our players, fans, the entire Celtics organization, and my family for letting them down," Udoka said in a statement released to ESPN. "I am sorry for putting the team in this difficult situation, and I accept the team's decision. Out of respect for everyone involved, I will have no further comment."
Udoka, 45, is considered one of the top up-and-coming coaches in the league. In his first season as coach of the Celtics in 2021-22, he led them to a 51-31 record and the Eastern Conference championship before losing to the Golden State Warriors in the Finals.
WHO IS IME UDOKA? Suspended Celtics coach was considered one of NBA's top young coaches
MEET JOE MAZZULLA: Who is the Celtics' new interim head coach after Ime Udoka's suspension?
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The Celtics were 23-24 on Jan. 21 and won 28 of their final 35 games, finishing with the second seed in the East. Boston beat Milwaukee in seven games in the second round and beat Miami in seven games in the conference finals.
Udoka is credited with installing a defense-first mentality and players bought even into his fiery and demanding style. He isn't afraid of yelling players during a game or criticizing their play to the media after games.
He finished fourth in coach of the year voting, and the Celtics are expected to contend for the conference championship again this season with a core of Jayson Tatum, Jaylen Brown and Marcus Smart.
This is devastating for Boston as franchise and as a team trying to win a championship. The Celtics have thrived on continuity, and that has been disrupted. It's been decades since the Celtics had a person coach just one season. Satch Sanders took over for Tommy Heinsohn in 1977-78 but lasted just 14 games the following season.
After Tatum, Brown and Smart, the Celtics have Al Horford, Grant Williams, Robert Williams, Derrick White and Payton Pritchard back from the conference championship team and added Malcolm Brogdon and Danilo Gallinari (injured) in the offseason.
But getting back to the Finals with an interim coach amid this scandal in a deeper Eastern Conference just became more difficult for the Celtics.
This article originally appeared on USA TODAY: Ime Udoka suspended by Boston Celtics for entire 2022-23 NBA season