It's year by year. Two years they were 25th. And thier YPC was 29th this year. Plus nobody defends the run against the Lions since they are scared of Calvin. It's favorable boxes and still bad YPC or average YPC. That is the worst run support in the league and forced to pass against tough pass defenses. The coverage on Calvin makes it harder on Stafford. Really we should just hand it off and kill teams by running but we couldn't due to injuries and some bad blocking (Raiola/Sims).
But I would say 2012 and 2013 problems were due to weapon injuries, drops and fumbles lost (not as much run support those years). Plus defensive problems. 2014 it was run support and protection for sure issues.
And it's not just run support. Almost category beyond Stafford's control was bad other than pressure 2012/2013 and turnovers/defense 2014. When he got a little support in 2014, they pulled off 11 wins. the offensive stats will show good things too when the run support, drops, protection, experience in the system come around. That should be 2015.
+ turnover differential. 10 and 11 wins. As long as we don't shoot ourselves in the foot and not turn it over, the Lions win double digit games.