I think you might be a little confused. It is a contact sport but it isn't in a battle arena. It's called a the sphere. It's not a creative name for a sphere of water but that is the playing field for the game.

There are 6 players on each team. A goalie who protects the goal. Two defenders that defend the goal. Two offense who shoot towards the other teams goal and then a mid fielder who helps pass the ball between players to score.

You use skills and strategy to score with the Blitzball. If you run into someone they will try to tackle you to get the ball.

I hope that makes sense.

-Yunie