Do you feel like introverts might be good athletes? I've noticed that since I've been playing "real soccer" (High school soccer), that I am really not the greatest player on the team. I feel like my wondering thoughts make me lose my ability to really focus on the game. Not to mention when it comes to making quick decisions on the field and lets not forget the talking/communication that is needed. Oh, and my team is pretty much extroverted, so that doesn't help matters much.
I personally never played sports much, though I can see how extroversion can be beneficial in a team setting. The thing about introversion is that introverts tend to watch and wait before acting, which in some sports (like soccer or basketball) where quick decisions are necessary, this can be harmful. But sports like golf that require patience and listening introverted characteristics can be hugely beneficial.