The 32-year old often-injured Czech defender struggled to have an impact at Craven Cottage last season since his move from Juventus in the summer but Jol clearly has plans for him for the upcoming campaign.
"Grygera was injured and looks better now," the Dutchman told The Chronicle.
"Hopefully he can prove himself before the end of August. If he proves he's fit I would like to keep him.
"He was one of the few players who did well from the start. I played him against Chelsea in the Carling Cup and he was the best man on the pitch. He's a good player."