Kansas City Chiefs wide receiver Juju Smith-Schuster took a nasty helmet-to-helmet hit in the first half of Sunday’s victory over the Jacksonville Jaguars, a collision that knocked him out the game yet it went unpenalized despite one official dropping the yellow flag at the conclusion of the play.

With just over six minutes left in the second quarter, Smith-Schuster caught a pass from Patrick Mahomes on third-and-4. As he turned around to run, he got bulldozed by safety Andre Cisco, who looked like he was trying to lead with his shoulder. He clacked helmets with Smith-Schuster, which you can hear on the broadcast.

As soon as he hit the ground, Smith-Schuster appeared to be having a fencing response, which is when the arms and hands flex unnaturally in response to brain trauma. Miami Dolphins quarterback Tua Tagovailoa had a fencing response when he sustained a head injury several weeks ago.

An official threw a flag on the play, but it was eventually picked up and a penalty wasn’t called. The penalty seemed obvious, because helmet-to-helmet hits aren’t allowed in the NFL, but the flag may have been picked up because Cisco didn’t obviously lead with his helmet. The official may have judged the contact between helmets as incidental.

Several Chiefs players were livid about the no-call after the game, including safety Justin Reid.

"We were mad. I’ve had a lot of big hits and not once have I made helmet-to-helmet contact like that," Reid said, via ESPN.

Quarterback Patrick Mahomes was right with him.

"Obviously there was some helmet-to-helmet contact, and we want to get that out of the league as much as possible, for player safety," Mahomes said, via ESPN. "These guys on defense are playing too, but by rule, if it’s helmet-to-helmet, it is supposed to be a flag.

"I know that guy wasn’t trying to. I know it’s a bang-bang play … It was scary when you’re out there. We saw him after the game and he seemed perfectly normal, giggling around, joking around, stuff like that. Just take precautions and get him back healthy as quickly as possible."

Smith-Schuster stayed on the ground for a bit, but was awake and able to leave the field with assistance. He immediately entered the concussion protocol and was ruled out for the remainder of the game.

"As long as there’s contact to the head, it doesn’t need to be in the game," Chiefs coach Andy Reid said, via ESPN. "So it looked like there was contact to the head from where I was standing, but I’m not the one making the call."

JuJu Smith-Schuster of the Kansas City Chiefs
Chiefs wide receiver JuJu Smith-Schuster was down on the field after a scary collision with Jaguars safety Andre Cisco. (David Eulitt/Getty Images)