The NFL and the NFL Players Association are reviewing a potential breakdown in the league’s concussion protocol after New England Patriots safety Patrick Chung took a hit to the head in the first half of a 31-20 loss Sunday against the Jacksonville Jaguars.

“A joint review by the NFL and NFLPA of the application of the Concussion Protocol regarding New England safety Patrick Chung during the Patriots-Jaguars game is underway,” a league spokesman confirmed in an email to USA TODAY Sports.

Though it is not conclusive when Chung sustained a concussion against the Jaguars, one apparent helmet-to-helmet collision with 12:54 left to play in the second quarter may have been the moment.

On a second-and-8 rush to the left, Chung engaged with Jaguars tight end Niles Paul, who was serving as a lead-blocking fullback. Chung and Paul crashed into each other, tumbling to the turf. Running back Corey Grant earned 1 yard on the rush, but Chung stayed down, and was caught by the CBS broadcast grabbing his face mask and shaking his helmet – both of which could be possible signs of a concussion.

He stayed down momentarily, forcing umpire Barry Anderson to blow the play clock dead for an injury timeout. Chung then popped up to his feet and appeared to talk briefly with Anderson.

Anderson then pointed to the sideline to apparently remove Chung from the game. Chung stayed on the sideline for one play and returned for the following snap.

Chung then played sporadically for the Patriots, until a third-and-3 with 14 seconds left in the half, when he ceded a touchdown in coverage to Jaguars tight end Austin Seferian-Jenkins. In the play, Chung was picked by Jacksonville receiver Dede Westbrook, but no penalty was called.

That was his last snap of the day, and when the Patriots returned from the locker room after halftime, Chung was not on the sideline. The Patriots later announced he had suffered a concussion.

The potential breakdown in the NFL’s concussion protocol would have taken place if Anderson had felt Chung was unfit to continue to play, and the safety had not gone through the league’s proper sideline concussion assessment.

The NFL has previously dealt with failures of the concussion protocol, most notably when it announced breakdowns in a November 2015 hit on then-St. Louis Rams quarterback Case Keenum and a Dec. 2017 hit on then-Houston Texans quarterback Tom Savage – both of whom were allowed to reenter their games after suffering significant blows to the helmet.

Follow Lorenzo Reyes on Twitter @LorenzoGReyes.