The Mali international has been sidelined for most of the campaign with a knee injury and although Jol says his return is not imminent, he hopes to have him back before the summer.
"Diarra is still not right," Jol told the Fulham Chronicle of the man who joined last February. "He will need quite a while to come back, hopefully before the end of the season.
"He had an operation, looked better and then had a rest and it was even more painful.
"Hopefully in the next couple of weeks we will know more."