Ian Crook says he quit as Sydney FC head coach after the pressure of the job started to affect his health and he realised he wasn't the right man for the high-profile role.
Crook quit suddenly on Sunday after just six matches at the helm of the A-League club.
Assistant coach Steve Corica will step in as caretaker until a replacement is found.
Crook's departure comes after the Sky Blues suffered their second painful loss in the space of a week, surrendering a two-goal lead to lose 3-2 to arch rivals Melbourne Victory at Allianz Stadium on Saturday.
That loss followed last week's 7-2 thumping by Central Coast.
Crook said he had "not been feeling well for weeks" as he struggled to deal with the pressure and media spotlight associated with the role, all of it magnified due to the arrival of Italian superstar Alessandro Del Piero.
"There's a huge amount of pressure on this job and I think you have to be a certain type of person to take it on," Crook said.
"I don't regret it but I don't think I'm the right type of person."
Crook said he struggled with the off-field side of the job
"I think it's something that just builds up on you as an individual.
"What I love is out on the pitch, probably all of this (media attention) has become a bit of a burden.
"That's become a bit of weight on my shoulders to be honest with you and I probably haven't handled it very well.
"The minute it started to affect me health-wise, that's when I started to question it."
Crook admitted after the loss to the Victory he was feeling under pressure and he was also involved in a heated argument with fans, who criticised him for substituting Del Piero off in the second half.
After a long discussion with his wife later, Crook sent a text message to Sydney chief executive Tony Pignata at 1.30am on Sunday morning before meeting with him at 8am to deliver his shock resignation.
He said he wanted to do the right thing by everyone and hoped to stay involved with the club in some capacity.
"For me it's not about quitting, it's about doing the right thing for everybody, because the club have been fantastic to me," Crook said.
The Sky Blues are now on the hunt for their seventh head coach in eight seasons of the A-League.
Englishman Crook was appointed at the start of the season after the Sky Blues missed out on their top target, Central Coast boss Graham Arnold.
Corica's first assignment as caretaker coach will be a trip to face an out-of-form Brisbane Roar at Suncorp Stadium on Friday night.