Chairman of football Adam Pearson admitted "a long year has taken its toll" after Paul Jewell resigned as Derby manager.
Jewell's departure had been widely anticipated after his failure to attend a post-match press conference following yesterday's 1-0 home defeat against Ipswich.
After taking over from Billy Davies last November with Derby bottom of the top flight, Jewell could not prevent the club going down as the worst team in Premier League history as they were relegated with a record-low 11 points.
Having failed to win any of his 24 league games, Jewell brought in 13 new players in the summer but they still made a poor start to life back in the Championship, taking five matches to win.
The 1-0 home defeat by Ipswich was the last straw for Jewell, who won just seven of his 50 league games in charge and lost 30.
Pearson told Sky Sports News: "It is disappointing. We had a chat after the game and Paul felt it was in the best interests if the club went in a different direction.
"That is what we agreed to do but Paul had the club's best interests at heart. It's been a long year and it has taken its toll and we must now move forward without him.
"Paul has got a proven track record and he deserved time on the back of that record. I think he felt things were conspiring against him and perhaps he just needed a fresh chapter.
"The pressure has been on Paul all season because of last year and what happened. There was a big hangover at the start of the season but Paul did everything in his power to get rid of that. He worked hard during the summer but we made a slow start which put the pressure on.
"I enjoyed working with Paul, he is a tremendous manager and I hope he goes on to have a fantastic career. He did not want to see the club struggle and he has done a very honourable thing to tell me that."