Chris Polk inactive for Eagles, leaving Sproles and McCoy as club’s only backs

Despite practicing fully all week with a hamstring injury, Eagles second-year tailback Chris Polk is inactive for Sunday’s game vs. Jacksonville, the club said this morning. With Polk out, the Eagles have just two active tailbacks: LeSean McCoy and Darren Sproles. McCoy is already a universal starter in fantasy leagues. And Sproles’ stock gets a…