Tottenham are eight points behind United having played a game more and need to win at White Hart Lane to remain in real contention, in a campaign where they have also impressed on the European stage.
Ferguson credits their success to the ability of Redknapp, playing an expansive brand of football that is in keeping with Spurs' cherished tradition.
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The north London side have proved themselves capable of taking any team apart on their day - most famously against Inter Milan in the Champions League in November.
In adding that experience to the FA Cup he won at Portsmouth, Redknapp has fulfilled all the criteria which had previously been cited as reasons why England could not be coached by an Englishman.
Ferguson believes it is down to Redknapp's straightforward approach to his job.
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'Harry's great strength is his common sense management,' said the United chief. 'He doesn't confuse issues. He is a good judge of a footballer and is straightforward in what he demands of them.
'That is down to the experience he has gathered over the years. Common sense management today is not a bad thing to have.'
Ferguson admits it is a long time since Spurs have enjoyed such good times.
'Traditionally, Tottenham are one of the really good football clubs, with a proper philosophy of the game,' said Ferguson.
'Unfortunately you have to go back to 1961 when they had their great team under Bill Nicholson.
'They were the first team to win the double after the war and won the FA Cup the following year.
'They were exciting and had an incredible team with really magnificent footballers, like Danny Blanchflower and Dave Mackay.
'Tottenham are always going to be well regarded because of that great period. That is the standard they have always had set for themselves and is why there has been such great disappointment about not winning the league since then.'
Contending for the Barclays Premier League crown seemed a distant ambition when Redknapp arrived at Spurs.
With Martin Jol disposed of less than 18 months after getting Spurs to within a final-day win over West Ham of a Champions League place, the Londoners collapsed dramatically under Juande Ramos and were more in danger of relegation than breaking that top-four cartel.
'The turnaround since Harry went there is quite startling,' said Ferguson. 'Their performance level this season, allied to it being their first time in the Champions League, has been excellent.
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'But the test for them will be when they combine being back in the Champions League in February and March with the challenge of the league and the FA Cup.'
It leaves United facing what Ferguson describes as their 'biggest test' so far, the first in a sequence of tough-looking away games that will almost certainly shape their season.
With that knowledge, the Red Devils could not be picking a better time to welcome back Wayne Rooney after a two-match absence, whilst skipper Nemanja Vidic and veteran goalkeeper Edwin van der Sar are also expected to return to the side that defeated Liverpool last weekend.
Redknapp has already stated his belief that United will not emulate Arsenal's 'Invincibles' by completing the entire campaign undefeated.
Ferguson does not view that as an attempt to undermine his own team, merely another example of his friend's down-to-earth approach.
'There is nothing exceptional in that comment,' he shrugged. 'Harry is just echoing what I have said all along. There will be a blip. But can you tell him I don't want it to be on Sunday?' David Beckham was never going to play for Spurs against us insists Sir Alex FergusonManchester United starlet Corry Evans joins Hull on loanAll the latest Manchester United news, features and opinionAll the latest Tottenham Hotspur news, features and opinion
Explore more:People: Alex Ferguson, Nemanja Vidic, Danny Blanchflower, Harry Redknapp, Wayne Rooney, Martin Jol, Edwin Van Der Sar Places: Liverpool, London, United Kingdom