Just a legality question.
I'm based in Canada, and may be shooting for a sports association. I will shoot the players on an occasional basis and the images would be displayed on their website, and I would have a link back to my site.
For releases and the such, since the images would be on their website who has to worry about getting the permission?
I would think that the organization already has that covered by their agreement with the players. There is typically a form to sign when you are a player/member of such an organization that, in addition to the usually insurance liability waivers, also has release language regarding images.
This is really a question for your client. They would be in the best position to respond accurately, no?