Crowding 101-
This is something I see in all levels of play. When an opponent is getting into your line of vision here is an old school trick. Cross the line of vision between your opponent and the ball but it has to be done early and not late. Move too late, and it is a rally hinder. Move early and the movement puts you in better position and the opponent will be aware of your position. This puts the opponent under more pressure.
Another trick I see being employed (consciously or unconsciously) is restriction of the follow through because one player getting too close. Player B is on player A’s shoulder so player A restricts her or his swing. Player B needs a lecture regarding follow through or a strong ref.
Try this for Player B-get bigger with setups. Take up room and a full backswing to swat that pesky player away. Make them give you the room and then take your swing on setups. Left one up? Got a player getting big, following the advice aforementioned?
Well then, get skinny! Get large and get little for good offensive and defensive positioning!