At this point I would be surprised, for sure, if he reached his potential.
I did hear from a very valid source, that Marcel was really influenced by Mario, and held him in huge regard as soon as he got to Buffalo, and (this is my reading of what was told me) Mario basically fukked him because Mario became a malcontent and locker room lawyer and Marcel was influenced by all of that nonsense.
Surely not an excuse. Surely Mario has been gone for a year and a half. But I could see that happening. I have given Marcel the benefit of the doubt too many times. He clearly needs to clean up his act and game and start to earn that paycheck. But I think that did likely play a part in his lethargic play the last couple years.