Bolat could well be the first new addition after finishing up his rehabilitation from a cruciate ligament injury at Fulham.
"He will have a free transfer in the summer," Jol said. "We wanted to take him last summer but he had this injury.
"He wanted to do his rehab with us, his club gave him permission to do that and he is fit now. Now it is a decision to take him or to leave it in January."