Harry Redknapp admits he informed QPR owner Tony Fernandes of his decision to resign in the early hours of the morning.
Redknapp has been told he needs replacements for both his knees and the 67-year-old cited his health as a key factor in his decision to leave Loftus Road.
"I was awake all night, thinking about it," Redknapp said. "I'm struggling so badly now. I can't walk, I can barely stand and watch. I'm in pain all the time.
"I've been putting it off and putting it off but it has got to the stage where I cannot do the job."
Redknapp continued: "I went to bed thinking I would sleep on it, but then I couldn't sleep a wink.
"That's when I decided to call Tony. It must have been 5.30am. I just told him he needed someone who could properly coach and manage the team in the next 10 weeks. It's such an important time. They need someone who can give it everything."
