No Brain Surgeon answer here but maybe his shoulder hurts when he runs . I know I'm just kickin the tires here but I'd bet a lot I'm very close. Even though the Dr's and trainers have cleared him. As a past multiple surgical patient ,I know sometimes it still hurts like Hell when the Dr. says your fine and you are still hurting while your running your routes and its just not like it use to be before you SHREDDED your shoulder into a pulled pork sammy.

NO INJURIES!!!