Du Preez was set to see a specialist on Monday night to assess a torn pectoral muscle he suffered during the team’s 41-22 defeat to the Hurricanes at the weekend.
That leaves coach Robbie Fleck with no recognised No.10 in the squad with Jean-Luc du Plessis and Kurt Coleman still out and Damian Willemse set for the U20 World Cup next month.
Dillyn Leyds has trained at first receiver for the Stormers before and could the natural fit for the role.
Du Preez is expected to be out for at least three months, even if he doesn’t go under the knife.
He joins centre Dan du Plessis and flank Cobus Wiese, who both dislocated shoulders on tour, on the long-term injury list.
Luckily for Fleck, the Stormers on a bye this weekend ahead of next Friday’s visit of the Blues to Newlands so he can think about his flyhalf problem.
And there was some good news on the injury front.
Centre Damian de Allende (ankle) and wing Seabelo Senatla (foot) will both return to full training this week after lengthy layoffs.
De Allende makes a welcome return to the squad after missing the entire season so far and follows his Springbok midfield colleague Juan de Jongh, who returned to fitness last week, back into contention.
Bok locks Eben Etzebeth (calf) and Pieter-Steph du Toit (knee) have recovered from minor niggles and are also available.