Jol pulled off quite a coup in tempting Berbatov to Craven Cottage over the summer, with the enigmatic frontman making a move from Manchester United.
The Bulgarian forward shone during the opening weeks of the 2012/13 campaign, but he has now gone seven games without a goal as the Cottagers have tumbled down the Premier League standings.
There is a danger that Fulham could be dragged into a basement battle if they are unable to turn things around, and Jol knows appreciates that getting the best out of Berbatov will be crucial to their efforts.
He said: "If things are going well then everyone will be happy with him but if things are not going well then he can be unhappy.
"He is used to winning games at the clubs where he was so we have to talk to him. He has to put in the same attitude and work-rate that he always did before.
"When he does that there is no problem, but he is certainly a player who we have to keep on his toes. We hope he does well for us because we were very happy with him for the first few months.
"If we don't pick up the results we'll be in the same situation as five or six other clubs."