"I led the NFL in attempts the past two years and they really didn't go out and get a quarterback to help me, so I knew it's going to be all on me again," Williams says in the documentary, which premiers Friday. "I could see my mortality as a football player, that I'm not going to be able to do this much longer. It just became obvious to me that playing football for me is not going to be fun, not something I'm going to enjoy and it's time for me to do something different."