Too much wine used in coq au vin
Marinades are generally surface treatments, especially in thicker cuts.  With the exception of salt (if any in the marinade), I doubt your chicken has absorbed any marinade. So, your issue is the higher quantity of liquid, and flavoring of the wine.  I think you could go either way...remove some, or reduce.  If it were me (so as not to be wasteful), I would just cook as normal, reduce longer, and taste and re-season along the way.