5:57 PM ET

The spotters assigned to watch players for concussions were aware of the possibility of a head injury to New England's DeVanteParker.

According to the league and the players' union, the spotters didn't have to ask the officials to removeParker for a concussion evaluation because Arizona threw a challenge flag.

The officials reviewed the medical staff reports and game video to understand the sequence of events in order to make the determination.

The review was started because it appeared that Parker may have been allowed to play despite having a concussion. The game-day concussion checklist was followed, according to the parties.

According to the documents and interviews, one of the spotters was talking to New England's medical staff about a previous injury. The other certified athletic trainer spotter heard the broadcasters commentary in real time and immediately informed his colleague of the need to review the play for a head injury.

During the 20 seconds that elapsed before play was stopped, both spotters requested the replay, reviewed the game video to confirm the player received an impact to the head and decided a mandatory evaluation was necessary.

When the game was stopped because of the challenge flag, the spotters were in the middle of calling a medical timeout. The player was removed from the field and evaluated for a concussion after the spotters told the medical staff.

Even if the Cards had not challenged the play, the union and the league were satisfied that Parker wouldn't have played in another play. Players were praised for pointing out the injury.

He missed last week's loss to the Las Vegas Raiders and won't be in the lineup for Saturday's game.

This report included information from The Associated Press.