Warnock was replaced at Loftus Road by Mark Hughes, but the former Wales manager was sacked early this season, with Redknapp taking over.
Warnock was in charge of the QPR side that gained promotion to the Premier League in 2011, but was sacked at Loftus Road after a poor run of results in January 2012, with the club avoiding relegation on the last day of the season.
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"We were told, keep out of the bottom three until January, and then you can bring in three or four players.
"We did that and then, to get to January and not have an opportunity to do that, is disappointing."
Warnock went on to manage Leeds United this season, but resigned with six games to go after failing to secure a place in the playoffs.
But the 64-year-old Yorkshireman insists he is not bitter about Fernandes' decision to let him go, despite his insistence that it was a poor decision on chairman's part.
"It's your club, you're entitled to do what you want, and they decided to go in a different direction," Warnock continued.
"They'll have got a lot of advice, from a lot of people outside, saying you've got to change your manager, and all sorts of things.
"Only time tells if it's the right decision and I don't think it was."