The NFL Players Association is investigating the Carolina Panthers after linebacker Nic Scourtons season-ending ACL tear last week.Scourton went down on the very first day of the Panthers training camp on Thursday. Because the injury happened so quickly into camp, within the mandatory five-day acclimation period, the union has started the investigation.In theory, teams should be easing players into training camp so as to avoid major injuries like this. The current collective bargaining agreement does not allow live contact during the first five days of camp, and does not allow on-field activities other than running and conditioning.The players associations investigation will determine how Scourton went down with his ACL injury specifically. Its unclear what punishment the team could face here should a violation of the CBA rules be found.The Panthers are aware of the inquiry and are cooperating with the NFLPA, a team spokesperson told the Charlotte Observers Mike Kaye. A timeline for the investigation is not known.While the timing is rough, and has led to an investigation, the Panthers dont think the injury was anything other than a simple accident.It was really just unfortunate for Nic. Hes a really, really good player, Panthers tight end Tommy Tremble said on Sunday, via The Athletics Joe Person. What happened was just a freak accident, and I feel so bad for the kid because he worked his butt off this offseason and I think this was gonna be his best year yet. I dont think it was anything on anyones tempo, everyones just trying to get better every day. It was just an unfortunate thing to happen at practice It kind of sucked the life out of us when we saw it happen.Scourton was set to enter his second season in the league this fall. He had 47 total tackles and five sacks last season for the Panthers, who selected him with the No. 51 overall pick in the draft last summer out of Texas A&M. He was set to be a significant piece for the Panthers defense this season alongside new pass rusher Jaelan Phillips.The injury was just the latest significant one that the Panthers have been hit with in recent days. The Panthers lost starting right tackle Taylor Moton due to a blood clot, and both starting defensive tackles Tershawn Wharton and Bobby Brown III, and cornerback Jaycee Horn all started on the non-football injury list.The Panthers, who won the NFC South last season for the first time since their Super Bowl run during the 2015 campaign, will open the year against the Chicago Bears on Sept. 13.