"It is a bad one for Franck," Fulham boss Chris Coleman has said.
"We were disappointed with the challenge even though I don't think the guy meant to do it, but he got it wrong.
"We are looking at three weeks to a month out for Franck because the gash in his ankle is so nasty.
"We've got nobody else who can play centre-half and it looked at one time as though we might have to play big Dave Beasant (the club's goalkeeping coach and former Wimbledon, Chelsea and Newcastle goalkeeper) at centre-half on Wednesday."