Make relation of custom taxomies

You can use taxonomy term meta for that. Like you said you have “team” and “player” taxonomy. Now you can add a taxonomy term meta on “player” taxonomy’s terms and save the “team” terms(where the “player” belong) ID on that “player” taxonomy term meta. Then get the the player based on that “team” taxonomy term ID taxonomy term meta. By this way you can make the relation between “team” and “player”.

Here you’ll find a class, by that you can add taxonomy terms easily. And do some google to get the way to filter taxonomy terms based on term meta.