The former Sheffield United and Crystal Palace manager said he was close to leaving Loftus Road after his side were hammered 4-0 by Bolton on the opening day of the season.
Warnock was frustrated with what was going on at the club, both on and off the field, and disappointed they had failed to push on after winning the Championship title while operating on a shoestring budget.
But the Rangers boss says Fernandes was key in keeping him at the club.
He told the Daily Star: "If Tony hadn't had arrived I would have left after that 4-0 defeat to Bolton.
"I am being honest here. I didn't want to leave after what I had achieved but things needed changing. I was ready to go.
"Tony arrived and it's a whole new game. I signed players who were once totally out of our wage limit. I also signed players who still had something to prove, the type of people who I have always gone for.
"For once I could shop in Harrods and not Woolworths. For once I could be on a level playing field with the others."
"Now I will be very disappointed if I do go. I still have ambitions but I also know if we finish bottom I will be sacked."