Tottenham defender Anthony Gardner is set to be sidelined for six weeks with a hairline fracture of the fibula.
Gardner suffered the injury shortly after coming on for Hossam Ghaly in Sunday's FA Cup quarter-final with Chelsea.
He has had several injury problems already this season and Spurs manager Martin Jol admits the latest setback looks quite serious.
Gardner will be sent for another scan but an initial estimate suggests he will not return to action until the end of April.
If Tottenham get through their replay against Chelsea, Gardner would therefore miss the FA Cup semi-final against Blackburn on 14th/15th April.
"Anthony came on at Chelsea and after a couple of seconds took a knock to his knee," Jol confirmed on the club's official website.
"We'll do a CT scan but it looks like he'll be out for around six weeks.
"Fortunately, we have a squad of versatile players who can cover our defensive positions."