The Cottagers are currently on a run that has seen them claim just one victory in their last 11 games, sliding down the table into 14th position as a result and picking up just five points out of a possible 21.
With Berbatov grabbing the first goal against Southampton Wednesday, the 31-year-old forward was cautioned for taking his shirt off and revealing a T-shirt that had the message: 'Keep calm and pass me the ball', written on the front, a move that both puzzled and angered Jol.
"It was a bit stupid, and I will have to have a word with him," Jol said. "He probably thought he would get away with it as he never gets booked. It wasn't the brightest thing to do, but he wanted to make a statement.
"He tells the youngsters every day to play with confidence, keep the ball and don't be afraid. You need confidence and self-belief to play your football. He wants us to play in a certain style and that is the message he's trying to get across."
Fulham hosts Michael Laudrup's in-form Swansea side at Craven Cottage next up on Dec. 29, looking to turn its fortunes around.