He didn't fall out of favor with Marrone. The reason he became 5th string and subsequently inactive was that he can't play special teams, and he isn't as good of a WR as Watkins, Woods, or Hogan. Unless he makes a team with some really crappy WR talent next year, his career is over.
I never understood Bills fans' love for the guy. He quit on Syracuse, caused locker room problems in Tampa, and made his neighbors' lives a nightmare in FL.