Try to get your son involved in activities for which he has a natural talent, especially service projects in the school or community. Helping others will make him feel good about himself.
How about getting him a "coach," an older boy who does well in your son's chosen sport. This "coach" can mentor your son and bring his skill development up to a more competitive level. Being seen with this student will enhance your son's standing with his peers. Acceptance by a key person can make fitting in so much easier. Best of all, your son will gain confidence and improve at the sport, even if he does not make the team.
Contact the school counselor, teacher, or your physician about your child's depression. If he has become clinically depressed, he will not be able to take advantage of these suggestions -- or anything else you do to help. He will need professional assistance for a short time to physically and emotionally deal effectively with his situation. Continue to be a good listener and someone he trusts.