The Merriam-Webster dictionary defines hero as:
 ": a person who is admired for great or brave acts or fine qualities
: a person who is greatly admired
: the chief male character in a story, play, movie, etc.”
Seems to me that an athlete or any other person “who is greatly admired” can be called a hero. It’s perfectly ok if you don’t identify them that way, but others are just as reasonable for doing so.