The Red Devils finished second last season under Ole Gunnar Solskjaer but have fallen way off the pace since then and now sit seventh in the table.
Ralf Rangnick has been brought in as an interim boss until the end of the campaign with the German tasked with finishing in the top four and securing Champions League football.
Manchester City look to be running away with the title this season while Chelsea and Liverpool are head and shoulders above the rest of the chasing pack.
Defeat for United last time out to Wolves and reports of unrest in the dressing room has only made Rangnick’s job harder and Redknapp thinks he has a huge rebuilding job on his hands.
‘To be honest you’d struggle to find one of the current lot who’d have been a regular in some of the teams under Sir Alex Ferguson,’ Redknapp told The Sun ahead of United’s FA Cup third round clash with Aston Villa on Monday night.
‘Even keeper David de Gea — who has been their best player by far — but would you put him in ahead of Edwin van der Sar or Peter Schmeichel before him?
‘That’s how big the rebuilding job is for Rangnick. That’s why you can’t start blaming a manager who’s only been there five minutes.
‘Of course United could have a good Cup run, a few decent draws and you’re flying but a serious title challenge? That’s at least two years away, probably longer to be honest.
‘That’s why tomorrow’s FA Cup game against Steven Gerrard’s Aston Villa is huge for the rest of their season, which in itself shows how bad things have become.
‘In the past United would go for the Cup, of course, yet it was always a nice addition to what was usually a title or a Champions League challenge. Often both.
‘But could anyone be totally confident they would beat Villa? I certainly couldn’t say so.
‘And if those players are looking to blame someone for that, I’d suggest they start with themselves.’
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