NFLPA files grievance against NFL, Panthers for 'concrete-like' playing surface in Week 16, per report | CBS Sports Headlines NFLPA files grievance against NFL, Panthers for 'concrete-like' playing surface in Week 16, per report Multiple players took issue with the hardness of Carolina’s playing field ESN FeedsThis post was originally … Continue reading NFLPA files grievance against NFL, Panthers for 'concrete-like' playing surface in Week 16, per report