What type of dental crown would you recommend for a person that plays sports?

The answer is any crown will do but get a mouthguard to wear to protect that crown and the other teeth.  Protection is key!It is possible to make a sports orthotic to increase speed, strength balance etc.  I would Rx seeing a Neuromuscular Dentist for the best performance mouthguards but Underarmor also makes low tech performance mouth guards.The Pure Power Mouthguard is no longer available but a trained Neuromuscular Dentist can make you one that meets the same criteria.

There are many durable materials on the market, and your concern for the grey metal margin exists.  Insist on NOT getting a PFM, where the metal may show (now or as he ages).  At his age, he will likely need more than just this one in his lifetime.  He will also need a mouth guard, as the root of the tooth is weaker from the root canal and may fracture from an elbow when he is in the key.