Fulham still want to sign Marlon King, but only if Watford knock £1million off their asking price and accept payment by instalments, based on appearances, according to the Daily Mail.

The clubs agreed a £5m deal on Friday and King is reported to have already shaken hands on a £40,000-a-week contract at Craven Cottage.

But Fulham want to renegotiate the fee after it was reported that a medical had raised concerns about the Watford striker’s fitness.

One national radio station, broadcasting live from the Cottage before Saturday’s derby with Arsenal, reported King had failed the medical because of a knee problem. King missed most of last season with a knee injury.

Fulham boss Roy Hodgson, who desperately needs some firepower to boost his team’s attack, still wants to sign him but, wary of the Jamaican international’s injury record, now wants to pay £4m.

The club wants to be able to pay the fee in instalments, based on the player’s appearances to guard against losing money if his injury problems resurface.

Watford could be reluctant to sell at a reduced price, especially as King’s former club Nottingham Forest will receive 25 per cent of any fee following the sell-on clause they negotiated when they sold him for £500,000 little over two years ago.

Manager Aidy Boothroyd is now determined to get the deal done. He knows that, if it falls through, King returning to Vicarage Road could have a negative effect on the club.

A section of fans sang “Are you watching Marlon King” after Nathan Ellington put them 1-0 up in Saturday’s 1-1 draw with Charlton.

Boothroyd, who is waiting to sign Fulham striker Collins John as part of the deal, would not reveal why it has stalled but said: “I only hope it can be resolved for Marlon, for Fulham and for us.”