i remember reading somewhere about how the ranking is calculated.
It tracked back your last 15 weeks, including cup games.
So the idea being that if you are still in the cup, compared to someone not in the cup, you have more wins.
and something about wins against teams above you in rank were taken into consideration (obviously).
So if you beat a team below you, then you might not move in rank, but they might, therefore pushing other teams above them.