You do not have to be exceptionally strong in your sport to make some big time bucks through endorsement opportunities. Many believe that Anna Kournikova never deserved her mega deals and people are just coming around to accepting the fact that Danica Patrick may be legit (years after she first started raking in the dough through sponsorships and advertisements). Good looks, especially if you are a female athlete, could make you more money than the reason that you first were found: your ability to excel in your particular sport.
The latest case in point seems to be a young lady named Leryn Franco. Not only is she a javelin thrower, but more importantly for this discussion, her pretty face and stunning body will land her a topless gig in a new calendar. Obviously there is no mandate that you must represent somebody who is actually good in his/her sport in order to make money in this business.