Heyward, a former standout at Peachtree Ridge High School in the Atlanta area, signed with Georgia Tech after spending one year at Hargrave Military Academy in Virginia.
Gregory on Monday said Heyward tore his left anterior cruciate ligament on Thursday and will have surgery in the next two weeks. The recovery period usually takes up to a year.
Heyward enrolled at Georgia Tech for summer semester.
Gregory says Heyward's injury is "a temporary setback."