I just took a new job working with athletes. I have recently been working as a nutritionist with regular health-conscious people, with the occasional bodybuilder. So most of my experience is geared to these two genres. What kind of differences should exist between these diets and those of endurance athletes.
Depending on the type of athlete, the most likely challenge you will find is getting them to eat enough. Macro breakdowns are nice, but eating 5000+ calories a day can get old and finding creative and healthy ways to do this is quite difficult.
I'm working with basketball players right now (all of whom are too small and don't eat enough) and getting them to see the value of eating enough and making good food choices is about all I can get them to do.