Tottenham boss Harry Redknapp believes Manchester United still got a bargain price when they bought Rio Ferdinand for £30million in 2002.United scouted Ferdinand while he was a 17-year-old on-loan at Bournemouth and approached the wrong club about buying him, with the message eventually getting back to Redknapp at West Ham.Redknapp knew how good the centre-back was and told United he was unavailable but he left for Leeds in 2000 and eventually made it to Old Trafford two years later.Ferdinand is now as important to United securing another Premier League title as Cristiano Ronaldo is, according to Redknapp."When Rio plays he makes a massive difference," Redknapp said. "He's equally as important as Ronaldo as is."Rio shores it up a the back, gives them an air of confidence and is always in control, never looks flustered. Never seems to be at full stretch."Ledley King is like that and Alan Hansen was like that."Redknapp feels Ferdinand was a £30million snip from Leeds and is one of the key reasons why they will win the title this season, even if Spurs win at Old Trafford this weekend."United tried to sign Rio from Bournemouth where he was on loan," Redknapp said. "Martin Edwards (United chairman at the time) rang up Mel Machin at Bournemouth and asked if they would sell him but he said he doesn't belong to them. He probably would have liked to have sold him."So Martin rang me up, and I said he's not for sale, he hasn't got a price - £1million I wouldn't sell him."He'll be the best in Europe - in the end they had to pay £30million for him but that was money well spent for them. He's so quick."Redknapp nurtured Ferdinand at Upton Park and recalls the youngster quizzing him about the boots and diet of the first-team players, then establishing himself in the Hammers team.He was played in midfield and embarrassed Vinnie Jones with his close control in one match, before settling at centre-back.Redknapp never saw him as a penalty taker and last week Ferdinand missed a spot-kick in the FA Cup semi-final against Everton, with Sir Alex Ferguson's men now looking to bounce back and maintain their advantage over second-placed Liverpool."Liverpool have closed the gap from last year, Chelsea will be there again next year, Arsenal will get closer because they had bad injuries," Redknapp said.Plenty has been made of Ferguson's war of words with Liverpool boss Benitez, but the Spurs boss added: "We rely on players, the game's all about good players."Redknapp, however, conceded that United's rivalry with Liverpool will also be driving Ferguson."I think he would be gutted not to win it, especially with the rivalry with Liverpool and Benitez," Redknapp said. "They're red-hot favourites and I can't see them throwing it away."There's no love lost with Liverpool - I don't think he would be too happy losing it now."Meanwhile, Redknapp has left his options open if David Beckham wanted to return to England, even though sources close to the England midfielder suggest the 33-year-old wants to be at AC Milan next season."It's a million-to-one shot," Redknapp said. "He'd bring something to the football club."