Keane was dismissed following a tussle with Alan Shearer in the 4-3 defeat at St James' Park - and that same night he decided to take action.

The former Republic of Ireland captain said: "I went to bed but never slept a wink.

"Some time during the night I decided 'give it up Roy'. You've turned 30 - get out, get away, do something else.

"You've got to stop hurting yourself, hurting those you love."

In his autobiography, which is being serialised in the News of the World newspaper, Keane said he could no longer play on.

He also reveals he has a drinking problem and claims: "I had to stop drinking if I wanted to carry on playing."

Quitting the game, rather than drinking, had at one stage appeared the easiest option.

But Keane added: "I talked to my wife.

"She argued I would miss it. I said I wouldn't. Anything would be better than this madness, getting angry and frustrated, lashing out.

"I felt I'd lost the argument that some players were in the comfort zone. Too many people were content with what they had. It wasn't for me. I should go.

"Next morning I was waiting for Sir Alex Ferguson at the training ground at 8am. I told him I wanted to pack it in. He said it was a knee-jerk reaction."

Keane revealed the duo talked for a long time and he told Ferguson he would not play in the next game - the Champions League clash with Lille.

But Ferguson urged his captain to think again and Keane took his manager's advice.

Keane said: "On Sunday I walked our dog Triggs a long way, running the options through my head.

"Another club, somewhere sunny. At least I could be miserable in a warm climate.