Winger Duff limped out of Wednesday’s 1-0 defeat to Stoke City at Craven Cottage with a leg muscle problem.
Meanwhile, nineteen goal top-scorer Zamora missed the game as he continues to be troubled by an Achilles problem.
“Duff was taken off at half-time because he took a kick a while ago and we think one of his muscles was cramping up,” said Hodgson, whose side lost to an 83rd minute winner from Stoke’s Matthew Etherington.
“That was a blow of course. We hope it’s not too serious.
“I hope he’ll be fit for the final. There’s a week to go now. The medical staff don’t think it’s a muscle tear or anything like that.
“They think that it’s something to do with a kick he took a while ago which is switching off the muscle.
“Bobby stands a chance of making it but he’s not making vast amounts of progress on a daily basis so it could be touch and go.”