You could further segment each market by focusing on the buyers/users of the product or service. Admins, coaches, players, fans, parents each have different needs and opportunities to be addressed within these broader markets. As you mentioned GameChanger has done a great job at targeting coaches as the users and parents as the buyers. TeamSnap and Teamworks have also taken a similar approach by providing value to the athletes and the team administrators.
I think the biggest winners in the sports tech market will be those that provide major value to multiple user segments within a given market.