http://harvardsportsanalysis.org/2014/10/how-random-are-turnovers/
Conclusion in case you don't want to spend the time reading it:
So after a few hundred words of statistics, we arrive at a whopping conclusion that just over half of seasonal turnover differential is due to luck. That’s huge, especially when you consider that (from earlier) seasonal turnover differential explains over 40% of seasonal winning percentage.
At first glance, this does seem very high to me but evidence for this magnitude is the extraordinary year-to-year variability in turnover differential, which you would expect if luck was a mega factor as my analysis suggests. While starting quarterbacks absolutely play a role in turnover differential (Tom Brady throws fewer picks than Chad Henne) and tend to be fairly constant from year-to-year, nevertheless the correlation between turnover differential last year and this year is only 0.086 which is not significant at the 5% level.
Ultimately in a 16-game season, there’s just a whole lot of luck involved with winning football games and for all that commentators will talk about defensive schemes forcing turnovers this season, it’s just as important to be lucky as to be good.