Speaking ahead of tomorrow's Barclays Premier League trip to Old Trafford, Redknapp said his Tottenham team had closed the gap on United in the past year.

The Spurs boss was merely stating the obvious, having led his side to their highest ever Premier League finish of fourth last season, while watching Sir Alex Ferguson's men surrender the title to Chelsea.

But he was also echoing the fears of many United fans, who have seen their side become more vulnerable since the departures of Ronaldo and Carlos Tevez and the loss of form of Wayne Rooney.

"They are still great, but they're not as good as they were when Ronaldo and Rooney were in the team," Redknapp said.

"Don't forget they went to Arsenal last year and ripped them to pieces, so they are still an incredible side.

"But there's a big difference when you have Ronaldo and Rooney.

He added: "We're getting better, we're closing the gap and we'll keep improving."

As well as losing Ronaldo and Tevez and seeing Rooney struggle for fitness and form, United are having to deal with the fact many of their other great players are nearing the end of their careers.

Redknapp said: "(Ryan) Giggs and (Paul) Scholes - just two unbelievable footballers - (Gary) Neville, they can't go on forever.

"As good as they are - and they are fantastic still - they're not going to get any better now, are they?

"They may not be in their prime at 35, 36, or whatever, but they are still great players who would grace any team in the Premier League.

"But it's very hard to keep producing teams like that one with (David) Beckham, (Roy) Keane, Giggs, Scholes, Andy Cole, (Teddy) Sheringham, (Ole Gunnar) Solskjaer, Dwight Yorke."

In the past, Ferguson would regularly raid Spurs whenever he needed fresh blood, taking Sheringham, Michael Carrick and Dimitar Berbatov from them with alarming ease.

Those days are over, according to Redknapp.

"The chairman doesn't want to sell players that we don't want to sell any more," he said.

"We're talking about January; we're still trying to find maybe one player that would make the difference to us."

In the past, man-of-the-moment Gareth Bale would already be halfway to Old Trafford but Redknapp believes Spurs are now on a more equal footing with tomorrow's opponents.

That includes competing with them in the purchase of top players.

"I would never say Man United's an unattractive place; it's an incredible place to play," Redknapp said.

"I think Tottenham's an attractive place to come and play; we've got a new stadium coming, hopefully, as well."

Although Spurs have closed the gap on United, they have still failed to beat them in their last 22 meetings and have not won at Old Trafford for almost 21 years.

But with Rooney out injured, they will arguably have the marquee players on show tomorrow in Gareth Bale and Rafael van der Vaart.

Redknapp said of the latter: "It's a big stage for him, him and Luka Modric, people like that.

"We've got good players; they've got to go and play tomorrow and feel confident and make us play."

And although Spurs may have enjoyed little success against United, in Redknapp they have someone who has won there twice as a manager, most memorably with West Ham.

"(Paolo) Di Canio scoring there in the cup was a great day," he recalled.

"And also probably going there with Portsmouth and winning was a great day."

Redknapp will probably not get many more opportunities to put over Ferguson, with the 68-year-old nearing the end of his remarkable tenure at Old Trafford.

"It's the toughest job for anyone to follow without a doubt," said Redknapp.

"Some jobs, there's a good time to take them over.

"To take Man United over, you've got some act to follow."

But Redknapp does not see his fellow golden oldie quitting anytime soon.

"He doesn't look any different, really," he said.

"He still as bright as a button.

"He's lively, he loves his sport, he lives for his football, loves his racing.

"He's into all sport, isn't he? It's his life.

"So I don't see him slowing up at the moment."