Are there any player driven sports MMORPG's?

I was thinking it would be pretty cool if you were able to play with actual players in real time. Everyone plays their respective position, everyone participates. Basically, instead of clans, you have teams, all staffed by real players.

Your character is a player. You build his stats up through training, which could be small party quests/pvp duels. Depending on the sport, early gameplay could consist of training and pick up games to build up your character's skills and meet find other players you like playing with. Teams would have their own feeder leagues which is how you eventually prove yourself good enough for the majors (the equivalent of clan tryout servers). Core of the game revolves around teamwork and making friends.

As for more specifics regarding character development, I think an active leveling system like The Elder Scrolls/Fallout would work particularly well.

Regarding filling the positions on a team/preventing everyone from choosing the same "class," I would imagine the goal of playing on a professional team in actual games, versus being stuck in the minors because the position your in is oversaturated would be incentive enough.

I think this model could apply to really any major sport, except for maybe football (yes, I'm American, so, yes, I'm talking about American football). Having two de-facto teams for offense and defense really created a need for a large player base to fill those positions, versus just having the same players alternate between playing offense and defense.