Redknapp wrote in The Sun: "We then sent him out on loan to Bournemouth.
"And not long after, I got a phone call from the man who was Manchester United's chairman at that particular time, Martin Edwards.
"Someone from United had obviously seen Rio in action at somewhere like Stockport or Rochdale and advised him to get hold of this kid, who clearly had so much promise, from Bournemouth.
"But Bournemouth boss Mel Machin told Martin he was ours.
"I picked up the phone and Martin went straight to it, asking how much he would cost for them to buy and would we take a million pounds for him?
"I swallowed hard and then told him that Rio was not for sale at any price.
"He was only 16 or 17 at the time and yet his overall ability was such he was already being talked about as a million-pound player.
"I think that tells you everything there is to tell about Rio.
"He eventually got to Old Trafford via Leeds - and for a sum that was a lot more than a million quid."