Sunderland have confirmed that Dick Advocaat has stepped down from his role as club head coach and has left the Stadium of Light.
The Dutchman took charge of the Black Cats in March 2015 following Gus Poyet's dismissal and guided the team to Premier League survival with one match remaining.
Initially on a deal until the end of the 2014-15 season, he decided to remain at the club for an additional year, but they have struggled this time round, with three draws and five defeats seeing them slip into the league's drop zone.
Advocaat told Sunderland's official website: "I want to thank everyone who has stood behind me. This is a very special football club, with so many great people, but I feel it is the right time to do this - not for me, but for the club.
"I have made the decision to go after only eight games as I felt it was important to give everyone time turn things around - like we did last year. I am thankful to the chairman for understanding my feelings and I remain on good terms with everyone at the club."
In the press statement, Sunderland chairman Ellis Short added: "I am truly saddened by Dick's decision, but I respect him for his honesty and for doing what he feels is right for the club.
"He is a man of integrity and a true football person. He was hugely respectful of the club in taking this decision and he acted 100 percent in our best interests. It is also testament to his character that he has forgone any kind of a financial settlement, something which is very unusual in football.
"While this isn't a situation any of us envisaged being in, what is important now is that we regroup quickly and focus on the rest of the season."
Assistant head coach Zeljko Petrovic has also left the Stadium of Light.