The Wizards said Wednesday that Okafor's injury was diagnosed by an MRI after he experienced discomfort in his neck. The team said Okafor will begin rehabilitation to reduce inflammation and correct the injury but gave no timetable for his return.
Singleton was hurt during a voluntary workout at Verizon Center on Tuesday. He was scheduled for outpatient surgery to repair a fracture in the fifth metatarsal.
Okafor averaged 9.7 points and 8.8 rebounds in 79 games for the Wizards last season. Singleton averaged 4.1 points and 3.2 rebounds in 57 games.
The Wizards open training camp Sept. 28.