By Andrew Holleran Players complained about the playing surface in Carolina for last weekend’s game between the Panthers and the Lions. Now, an official grievance has been filed. ESPN NFL insider Adam Schefter reports that the NFL Players Association has filed the grievance. “NFLPA is filing a grievance against the NFL and Carolina for the hardness of the playing field in last Saturday’s Lions-Panthers game, per source. The NFLPA complained before the game and said the field conductions, in the extreme cold, only worsened as the game progressed,” he reported. Lions quarterback Jared Goff was a…