The Cottagers travel to Carrow Road to face Norwich with only three wins from their previous 17 league outings.
The 57-year-old manager is convinced that Dempsey's departure to White Hart Lane is a major factor in that dry spell, with the west Londoners missing the American's goals from midfield.
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|3/1||Bryan Ruiz is 3/1 with BetVictor to score at anytime against Norwich today
"Clint Dempsey scored all of our winners last year – and that was against the big teams as well," Jol told The Mirror.
"You need that quality. Wayne Rooney made the difference against us for Manchester United the other day and that’s what Dempsey did for us, too.
"You need players from midfield or wide positions who can score goals."
Dimitar Berbatov could be in line for a return, though, after missing the 1-0 defeat to Manchester United last week with a hamstring injury.
Fulham take on Norwich on Saturday, with the Canaries intent on getting revenge after a 5-0 hammering at Craven Cottage on the opening day of the season.