[DavidGilkes]

Will you be able to stand on the touchline? I ask because 200mm may not be long enough to get close to the action if you are stood behind the try lines or in the stands. AI mode means the camera and lens will continue to autofocus on the subject whilst it is moving.

Also, if you want to freeze the action, then you will need to push the shutter speed to 1/500 sec or faster. Increase the ISO for this if required.