(NewsNation) — 24 days ago, Miami Dolphins quarterback Tua Tagovailoa was carted off on a stretcher after getting knocked out. On Sunday night football, he is back on the field.

Tagovailoa said he’s glad to be back after a long process to clear concussion protocols.

It’s hard to forget the jarring scene on Sept. 29 in Cincinnati. Tua’s head hit the turf, his fingers twisted in front of his face, forced to be taken off on a stretcher and rushed to a hospital.

That happened four days after a fall against the Buffalo Bills, where he stumbled to get up, but eventually returned to the game.

In the weeks since, the NFL investigated his handling, then passed a sweeping revision of its concussion protocols.

Dr. Sara Gould, a doctor from the University of Alabama, where Tua played college football, said the concern here is if he’s hit hard in the head again.

“I think that’s what everyone’s very concerned about in the Tua situation because there was an initial injury,” Gould said. “And there’s concern that maybe he was still recovering from that when he was hit again. And so we want to watch out for that we want to be very cautious so that we don’t have our kids suffering second impact syndrome.”

It’s a very serious condition, and potentially fatal.

The NFL has never experienced a player dying on the field from a head injury and obviously wants to avoid that at any cost.

The new protocol put in place mandates any players showing ataxia — or visual head trauma — be ruled out of the game.

The NFL is also weighing possible game-day roster adjustments to help offset new concussion protocol rules — so teams don’t have an issue fielding a full roster if multiple players get ruled out.