Portsmouth boss Harry Redknapp has admitted he fears facing Manchester United with a depleted squad believing their quality will cause them serious problems in the absence of several key players.
Glen Johnson and Linvoy Primus, vital members of Pompey's outstanding back four which boasted five consecutive clean sheets at the start of the campaign, are injured and miss the match which will see United boss Sir Alex Ferguson celebrating 20 years in charge at Old Trafford.
Redknapp will be looking to strengthen his defensive back-up in the transfer window to avoid this situation occurring again.
Manager Redknapp said: 'We have done well this season but when you have to take some of your top players out it can be very different.
'It applies even to the likes of Chelsea. If they had John Terry and Frank Lampard out it would just not be the same team. It is all about good players.
'Linvoy and Glen have been outstanding this season and it is a big blow that we are without them at Old Trafford. You can get by in some games with players missing but with the qualities United have it is very difficult.
'Wayne Rooney is back in form which was inevitable, Cristiano Ronaldo and Ryan Giggs can relly hurt you down the sides and also drop into the hole behind the strikers. The list goes on and I think United have the chance to challenge Chelsea for the title this season in a three-horse race with Arsenal.
'But all I will say to my team is to remain positive, keep believing in yourselves - and enjoy it. We have 19 points from 10 games and if we can't have a go at United now, can't relax and play after the good start we've had, then we never will.
'One area where we are short is in defensive cover. I said a few weeks ago I might not have to bother with the transfer window in January and that would be a relief but now we find ourselves in a position where Matt Taylor is our only spare defender.
'He is playing wide left midfield and if we get another injury we could switch him to left-back - but that is all. It looks as though I'll be trying to sign one or two during the next window.'
Forward Benjani Mwaruwari and midfielder Gary O'Neil are also doubtful.
Veteran skipper Dejan Stefanovic's quick return from a torn cartilage - the tough Serb defender missed just one Premiership game - has boosted Redknapp.
Redknapp should call on Republic of Ireland international Andy O'Brien to fill in for Primus who has a hamstring injury and former Tottenham defender Noe Pamarot to replace Johnson.