Sunderland boss Sam Allardyce says Adam Johnson has "let everybody down" after the former England winger was found guilty of one count of sexual activity with a 15-year-old girl.
Johnson was cleared of another more serious charge, having already admitted to grooming and kissing her in a sexual manner, and has been told he faces a "substantial prison sentence".
Sunderland released a statement shortly after the verdict on Wednesday in which they stated they were shocked the former Manchester City man opted to change his plea to guilty on the two lesser charges prior to the trial getting under way.
Questions remain, however, as to how much the club knew, with Johnson's legal team claiming in court last week that Sunderland chief executive Margaret Byrne had access to Johnson's initial police interviews in May 2015, as well hundreds of WhatsApp messages exchanged between the pair. Johnson admitted kissing the girl and knowing she was underage in his first police interview.
The 28-year-old continued to play for the club until his sacking shortly after his guilty pleas at Bradford Crown Court. He will be sentenced later this month.
Allardyce told reporters at his news conference on Thursday: "I was aware of his plea on all the charges to be not guilty. On that basis he trained and played for the team if and when I selected him.
"Just before the trial started [and when Johnson changed his plea] it was a massive shock to everyone at the football club.
"The club took swift and direct action to dismiss him immediately."
Allardyce admitted it had been a trying few days for everyone at Sunderland, who are out of the Premier League relegation places on goal difference.
"It has been very difficult to try to judge what's going on because you want to know all the facts so you try to keep your cool until the judgement is made. Now, we all feel let down by what has happened and by what Adam has done.
"We certainly feel a lot of sympathy for the victim and her family. Justice has been done and he has let everybody down."