Medical staff tend to Tua Tagovailoa during a game September 29.
CNN  — 

Miami Dolphins quarterback Tua Tagovailoa told reporters Wednesday he was unconscious after being thrown to the ground during a September 29 game and doesn’t remember what happened to him immediately after his head struck the turf.

The chilling revelations came as the third-year quarterback spoke to the media for the first time since the injury, which came in a Thursday night game against the Cincinnati Bengals.

“Getting carted off – I don’t remember that,” he said. “But I do remember the things that were going on when I was in the ambulance and then when I arrived at the hospital.”

Tagovailoa’s injury, which was the second time in five days he left a game injured, pushed the NFL and the National Football League Players Association to review and update the league’s concussion protocol.

The investigation into Tagovailoa’s first apparent head injury in a September 25 game determined protocols had been followed but the outcome was not what framers of the policies intended. The quarterback returned to that game, then played four days later.

Tagovailoa told the media it’s been an ordeal.

“It’s been a process, that’s for sure. Having to deal with the interviews, with the NFL and the NFLPA and then, having to go and see doctors, outside, with second opinions… So a lot of it has been I would say pretty stressful,” he said.

“But all of it is done for player safety and I’m glad that I got to go through those things to understand more of the deals of concussions, and you know, the effects, long-term, short-term, things like that. I thought it was great I was able to go through that process and get cleared,” Tagovailoa added.

A concussion is a brain injury that happens after a hit to the head causes the organ to move back and forth inside the skull. But even after the brain itself stops shaking, there can be changes to the organ.

Neuroscientist Julie Stamm, a clinical assistant professor in the Department of Kinesiology at the University of Wisconsin-Madison, told CNN it can typically take 10 to 14 days after a concussion for the brain to get back to its baseline condition.

Tagovailoa was cleared to play four days after his first injury. NFL Chief Medical Officer Dr. Allen Sills said recently it is “extremely unlikely” a player in a situation like Tagovailoa’s would be cleared with the updated protocols. Sills said the median time for clearance is a nine-day window.

Tagovailoa is set to lead the Dolphins in his first game back since clearing the concussion protocol Sunday night at home against the Pittsburgh Steelers.

CNN’s Nadia Kounang and Steve Almasy contributed to this report.