Fulham defender John Arne Riise faces a spell on the sidelines

The extent of Riise's injury is not yet known, but Martin Jol says it is 'serious'

Fulham have suffered an injury blow with the news that John Arne Riise could face a lengthy spell on the sidelines.

The Norwegian defender was forced from the pitch as Fulham qualified for the Europa League group stages on aggregate despite a 1-0 defeat by Dnipro.

And Jol has admitted he could lose the player for some time.

"Riise has a serious problem with the leg," he said. "That's why I substituted him with Matthew Briggs."

The injury took the gloss from Fulham's progression to the group stages of the competition after a difficult night in the Ukraine.

They eventually won on aggregate after weathering wave after wave of attacks on a difficult pitch.

Riise joined the Cottagers in July, signing a three-year contract after leaving Italian side Roma for an undisclosed fee.

He has made six appearances this season - including both of the club's Premier League fixtures - but will now have to sit out with Briggs likely to get a run in the team.

The 20-year-old has impressed this term and was rewarded with a call-up to the England under-21 squad for their matches against Azerbaijan and Israel in September.