I don't want to go overboard on Marrone bashing. So I'll stick with facts on the record.
-Mike Williams and Marrone have a falling out while at Syracuse. The exact way it went is contentious.
-Mike williams averages over 800 yards and 7 TD a year with non optimal QB play in TB.
- In offseason of 2014 Mike gets traded.
-Mike Williams, despite his prior success cannot beat out Chris hogan on the depth chart.
- In four games, MW averaged 33.3 YPG. Hogan would average 26.6 all year.
Now, it's possible that Marrone's personal feelings played no part. But as Roman said recently (paraphrased) "the best indicator of future success is past performance". Several years of success preceded MW before he came to Buffalo. Even in a limited role he had better numbers than Hogan. His big TD against Houston showed the he was an able route runner, and had good speed to go with his size.
Personal opinion: either Marrone went entirely by football sense and got rid of a talented player because he was a bad judge of talent or Marrone let a vendetta get in the way of his team's performance. Either way, I see it as a mistake.