The Senegalese defender was on the brink of a return to first team action, having suffered a stress fracture two months ago, but he reported pain when stepping up his training programme.
Daf told the club's doctors that he was still feeling pain around the area, and tests have shown the injury is not healing as quick as had been hoped.
Sochaux, who have had a steady start to the season, are unlikely to be able to call on Daf until at least December.
