Dick Advocaat walked out on Sunderland after coming to the conclusion the squad was "not good enough" and admitted a relegation scrap was "not his cup of tea".
Advocaat's resignation was confirmed on Sunday, 24 hours after his final game of a seven-month tenure ended in a 2-2 draw against West Ham.
The Dutchman has cut a forlorn figure during the Wearsiders' abysmal start to the season - they have failed to win any of their opening eight Premier League games - and revealed he had made up his mind to go prior to the weekend.
He told Studio Voetbal: "I already made my decision last week. But the club asked me to do the match versus West Ham, and I really wanted to finish in style.
"The struggle against relegation is not my cup of tea. I think it was time for someone else to take over at Sunderland. I became negative, and that didn't feel like myself."
Advocaat initially moved to Sunderland in March with the brief of maintaining the club's top-flight status, a task he achieved with a game to spare.
Having initially refused the offer of a new deal, he was persuaded to sign a one-year contract after reportedly receiving assurances over the club's summer transfer budget from owner Ellis Short.
He added: "I don't regret signing my new contract, because it was a great experience.
"Our squad was simply not good enough. The club knew that we had to strengthen, but the chairman never told me how much we could spend."
