Sunderland chief executive Margaret Byrne has resigned following the Adam Johnson child abuse case.
Johnson, 28, faces four to 10 years in jail after being found guilty of sexual activity with a 15-year-old girl.
The Premier League club has been criticised for letting the England winger play after his arrest.
Byrne, chief executive since 2011, said that decision "was a serious mistake", with the club adding: "We are so very sorry for this."
In a statement, Sunderland said Johnson's victim had been "very badly let down first and foremost" by the player and "his despicable actions", but also "by the club they support".
"Mr Johnson lied to the club; he also lied to our fans and they have every right to feel aggrieved by this," it added.
