As the NFL prepares to celebrate defending Super Bowl champion Seattle and then make a much-anticipated debut in Melbourne, Australia, the league won’t be able to avoid some unsavory story lines. The NFL placed three players, including one who otherwise might be starring in that marquee opener, on the commissioner’s exempt list to begin the season. Seahawks cornerback Terrion Arnold, Denver linebacker Jonathon Cooper and Green Bay running back Josh Jacobs are navigating serious legal situations that could keep them off the field for weeks, months or maybe the rest of the year.