Manchester United's resources may have made them the envy of world football but Sir Alex Ferguson has admitted a lack of defensive depth may cost them a fourth straight English Premier League title.

United are struggling to cope with a crippling injury list which has deprived them of six senior defenders in recent weeks - a scenario which, even for a club with their swollen bank account, has proved untenable.

Having already slumped to a surprise defeat at home to Aston Villa this month, United's makeshift back-line crumpled again on Saturday, as they were beaten 3-0 by Fulham at Craven Cottage.

Ferguson, having been denied the services of Rio Ferdinand, Nemanja Vidic, Wes Brown, Gary Neville, Jonny Evans and Edwin van der Sar through injury, cited his cluttered treatment room as mitigation for this latest loss.

"There's a fragility at the back at the moment and this was a difficult day for us all round," said Ferguson.

"With the way the league is, it's damaging and we just hope it's not the one that costs us the league.

"We need to start getting some of our players back to give us a proper chance. The guys are doing their best to get the players back, working overtime, but there's no light at the end of the tunnel.

"Maybe the fragile nature of the players at the back has given some of the others a reason to feel sorry for themselves."

Roy Hodgson's Fulham side have made a habit of bloodying the noses of the great and good in recent seasons and this was arguably their most impressive result ever in the Premier League.

"It's a mark of how far we have come," Hodgson said. "Our major ambition is to sustain the standard we have set.

"I would be wary to say we should try and raise the bar even higher. It's like the elastic band story - you can pull it so far and then it breaks."

At present, though, it is United's resources which are more likely to snap.