Darren Rovell makes a good point about the potential for Twitter endorsements. (I'll dub them "@ndorsements" and claim creation of the hot new phrase.)
But why limit it to athletes? In theory, anyone with a lot of followers -- the kind sports marketers are trying to reach -- would make for a good endorsement partner, especially if you're trading goods/services for a mention, rather than cash.
That could be sports-media folks or bloggers or anyone who might be considered a well-connected "influencer." They might want to start with Rovell himself! (Cough, cough: I'm always happy to offer my tweeted opinion on products I am given to test out.)