Ferdinand, 35, signed a one-year contract with the newly promoted west London club yesterday after being released by the Red Devils at the end of last season.
Redknapp, however, thinks Giggs would have extended the veteran defender’s career at Old Trafford had he, rather than Louis van Gaal, succeeded David Moyes after his spell as caretaker boss.
“[Ferdinand’s] a great role model,” the former Tottenham boss told reporters. “I signed him as a 14-year old so know him as well as anybody. I'm so pleased to have him at the club.
“Ryan Giggs told me if he'd been [Manchester United] manager this year Rio would have been his No.1 centre-half.”
Redknapp hopes to pair Ferdinand with Cardiff captain Steven Caulker, for whom QPR have agreed a fee, but admits they face competition for the 22-year-old’s signature.
“We've agreed a fee with Cardiff for Steven Caulker - they've got a couple of other clubs interested in him, but we're hoping to get that done,” the 67-year-old added.
“The chairman's been pushing it. I think he really wants to play with Rio Ferdinand. We're hoping it gets over the line.”
QPR have also offered Jack Collison, who left West Ham upon the expiry of his contract at Upton Park, a chance to train with their first team, and Esteban Granero has also returned to the club after a loan spell with Real Sociedad.
“Jack Collison is training with us,” Redknapp revealed. “He's a smashing boy and I'd love to help him out. He's a fine player.
“Granero has come back fit. He's a smashing lad, a good character. He wants to stay. Let's hope he has a good season.
“We need to bring in five or six. We need to improve the squad in terms of quality and numbers. [Chairman] Tony Fernandes knows what we need and I'm sure we'll get deals done. We're in the market for players.”