The departures of Moussa Dembele and Danny Murphy left a gap in the side's midfield and Jol received further bad news when Mahamadou Diarra was ruled out with a knee injury for six months.
Jol said: "As you know, when there was an opportunity with Karagounis we did that.
"There was an opportunity last year with Diarra and we did that. If there's an opportunity to get a good player in we will do that."
Due to Premier League squad restrictions, Fulham have the opportunity to sign three more free agents.