Once again, the effectiveness of the NFL's concussion protocol is being questioned. Once again, the NFL will investigate a team's handling of its star quarterback's injury.

This time, the incident in question occurred during the fourth quarter of a tightly contested playoff game between the Panthers and Saints on Sunday, when Panthers quarterback Cam Newton endured a hard hit to the head from Saints defensive tackle David Onyemata. Newton was slow to get back onto his feet. After doing so, he began making his way over to the sideline. But before he got there, he dropped to the ground.

Newton was replaced on the ensuing play by Derek Anderson while he underwent a concussion test on the sideline. He was quickly cleared to return to the game and upon his return, he threw a 56-yard touchdown pass to Christian McCaffrey to get the Panthers to within striking distance of the Saints. Ultimately, the Panthers' comeback attempt fell just short, which ended their season.

After the game, Newton said he suffered an eye -- not a head -- injury.

"I know it was precautionary things for a concussion, but it wasn't a hit to the head it was my eye," Newton said, per ESPN. "My helmet had came down low enough over my eyelid and it got pressed by the player's stomach, I believe. I thought somebody stuck their finger in my eye, but I've got my visor, so that couldn't happen."

Panthers coach Ron Rivera said something similar.

Still, according to ESPN's Kevin Seifert, the league has already contacted the Panthers' medical staff to ask them why Newton wasn't taken back to the locker room for further testing. As Seifert noted, the league changed its concussion policy late last month to "require a locker room concussion evaluation for all players demonstrating gross or sustained vertical instability (e.g., stumbling or falling to the ground when trying to stand)." Newton's incident appeared to fit the criteria listed above. 

He did not, however, go back to the locker room.

The incident comes during a season that has seen the league's concussion protocol come under intense scrutiny. In one notable case, Seahawks quarterback Russell Wilson was seen skipping a concussion test on the sideline before immediately re-entering the game. The league fined the Seahawks $100,000 for that incident. And then there was the incident that involved Texans quarterback Tom Savage when he was spotted twitching on the ground after a hit, but still briefly returned to the field before being yanked from the game. The Texans did not get fined by the NFL

This situation might be handled differently considering the Panthers diagnosed Newton with an eye -- not a head -- injury. And if it really was an eye injury, then the Panthers might have nothing to be worried about. But perception matters, and the perception in the moment was that Newton took a huge hit to the head, appeared to be wobbly, and was allowed to re-enter the game minutes later without a trip back to the locker room.

The NFL will now have to find out if the perception of the situation matches what actually happened.