Christian Damiano says playing on Craven Cottage's muddy pitch is like handing the opposition a 12th man.
The pitch cut up so badly on Saturday that it became difficult to pass the ball and, even though Fulham watered it just before kick-off, it didn't improve conditions.
Assistant manager Damiano said: "The pitch is so bad that for us it's like one opponent more.
"We want all the time to play on the ground, to build and play a good pass and create a good tempo, but it is difficult on this pitch.
"We water it before the game to try and help a little, but the roots are not strong and it is difficult.
"Hopefully in another month it will be better because the rain will help the roots bed in, but for us it is a problem."
Fulham's Craven Cottage playing surface was re-laid last summer. But it is believed that a lack of sun on one side of the pitch, plus the Thames being in such close proximity is causing groundstaff problems.
Manchester United announced earlier this week that their pitch it to be resurfaced again after suffering from similar problems, although they don't have the extra issue of a river being close by.
The Cottagers may well decide that any futher outlay at Craven Cottage would be a waste of money as the Whites move out to groundshare at Loftus Road next season.
Fulham have just five home league games left in the current Premiership campaign.