Redknapp has been doing battle with Ferguson for the best part of 20 years.
And he feels Fergie's retirement will leave a big hole in the game.
Redknapp said: "He will be a great loss to the league and football.
"He is a fantastic manager, but a top bloke as well who always had time for young managers if they phoned up - no matter what level they were at."
Redknapp is delighted for Moyes, believing the Scot to be ideal for the job.
He added: "He's the perfect choice and I think it is good that they have taken a British coach and have given him a chance. They have not just gone abroad but taken someone who has done his apprenticeship.
"It gives great hopes for everyone out there in all divisions."