Grounded starter causing my dead batt problems.

[Two560Two]

I have been trying to tackle an on going porblem with my benz. After about of a week to a week 1/2 of no usage, the battery gets drained. Replaced batter with a brand new one and still same prob. After my mech looked at my whole electrical system throughly, he concluded that my starter was grounded of which I dont know happened. My car starts perfectly fine since I now use the car everyday to keep the car from dying. Can a grounded starter or grounded whatever cause my dead batt problems? I insisited its something with my alternator but he concluded not. Any thoughts?