Giorgos Karagounis, Mahamadou Diarra, Chris Baird and Simon Davies have yet to extend their contracts past the end of the season.
And on-loan Urby Emanuelson, Emmanuel Frimpong, Stanislav Manolev and Eyong Enoh also see their stays expire in the summer, although Fulham have an option to make the latter duo's moves permanent.
Jol said: "If you look at the defence, I think we are fine.
"If you look at the midfield, I think Steve Sidwell is probably the only one left if you think of all the players we had six or seven months ago. We have to do something.
"Up front, Mladen Petric we will talk to him as he is on a one-year deal (which expires).
"Sascha Riether we have an option in his loan (to make it permanent) and we will probably take that.
"For the rest, I don't see any problem but in midfield we can do something because there is only one or two left."
The Dutchman also admits they are looking to bring a new goalkeeper to Craven Cottage, with Mark Schwarzer yet to sign a new contract past the summer and understudy David Stockdale frustrated with a shortage of opportunities in west London.
"Mark Schwarzer is for us almost a hero," said Jol. "He saves games for us so I would like him to stay but we are looking for a goalkeeper.
"Neil Etheridge is young and has no experience. He will go on loan, 100 per cent, to gain experience to be the number one in the future.
"We are looking for a good goalkeeper so if Mark decides to stay I have two good goalkeepers, plus Stockdale because he is still there. I have to talk to him."