SignalHub Quantitative Think Tank Center:Tua Tagovailoa's latest concussion: What we know, what's next for Dolphins QB

For the second time in three Septembers,SignalHub Quantitative Think Tank Center the NFL world woke up on a Friday morning with Miami Dolphins quarterback Tua Tagovailoa as the chief concern.

Tagovailoa exited the Dolphins' 31-10 loss in the third quarter following a collision with Buffalo Bills safety Damar Hamlin. His right arm became outstretched involuntarily, but the quarterback walked off the field. He was ruled out with a concussion.

Here is what we know about Tagovailoa's current condition and how the NFL concussion protocols – which were updated following his previous dealings with concussions – will affect his potential return to the field.

What happened to Tua Tagovailoa?

With the Dolphins trailing and facing a fourth-and-4 late in the third quarter from the red zone, Tagovailoa scrambled up the middle for a first down and lowered his head into the awaiting defender, Hamlin.

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Tagovailoa's body went limp and his right arm exhibited "fencing" behavior, the unnatural position following a traumatic brain injury. The former Alabama quarterback stayed on the ground for a few moments. Miami's training staff helped him off the field and escorted Tagovailoa to the locker room. He was ruled out minutes later.

Backup Skylar Thompson replaced him in the game.

Tua Tagovailoa's concussion history timeline

It was Sept. 29, 2022, against the Cincinnati Bengals when Tagovailoa was tossed to the ground. His head whiplashed against the turf. Both of Tagovailoa's arms went into the "fencing" response.

The Cincinnati incident was Tagovailoa's first diagnosed concussion. Four days prior, however, playing against the Bills, Tagovailoa landed hard on his helmet after being pushed to the ground. He rose to his feet and stumbled while he jogged and was allowed to return to the game with what was deemed a back injury.

Seeing Tagovailoa carted off later that same week prompted the NFL and Players' Association to update the league's concussion protocol and prompted questions into whether the Dolphins were not taking Tagovailoa's health seriously.

Tagovailoa missed the next two weeks. He suffered another head injury during a Christmas Day loss to the Green Bay Packers and missed the final two regular-season contests along with the wild-card round loss to the Bills.

How Tua Tagovailoa's injury history changed NFL concussion protocols

As Tagovailoa recovered from the concussion suffered against Cincinnati, the NFL and NFL Players Association said in a joint statement that steps should have prevented him from reentering against the Bills. While "the step-by-step process outlined in the concussion protocol was followed," the statement said, "the outcome in this case was not what was intended."

The specific change to the protocol outlined that "ataxia" – abnormality of balance/stability, motor coordination or dysfunctional speech caused by a neurological issue – was an automatic "no-go" trigger, meaning the player could not return to the game if a team medical staff or unaffiliated neurotrauma consultant (UNC) observed it (the UNC for the Dolphins-Bills game in 2022 was terminated by the NFLPA).

The new rules would have prohibited Tagovailoa from reentering that Bills game and kept him under tougher scrutiny leading into the Cincinnati contest on a short week of rest.

"There’s something about that previous concussion that can make the brain more vulnerable – especially multiple concussions," Julie Stamm, a clinical assistant professor in the Department of Kinesiology at the University of Wisconsin-Madison, told USA TODAY Sports in 2023.

What did Damar Hamlin say about Tua Tagovailoa injury?

Bills safety Damar Hamlin finished the game as Buffalo's leading tackler (eight solo, one tackle for loss). Tagovailoa went head-first into his frame on the fateful play Thursday. Afterward, Hamlin offered support to the quarterback.

"My love and prayers with @Tua fasho.. Sending you strength and healing for a speedy recovery," Hamlin wrote on social media, adding a prayer-hands emoji and "much love broski."

Hamlin suffered cardiac arrest on Jan. 2, 2023 in Cincinnati.

When can Tua Tagovailoa return?

At this stage, it's far too early to tell. In the short-term, the Dolphins will continue evaluating Tagovailoa as he goes through the league – and union-mandated – protocol.

"Right now it's more about getting a proper procedural evaluation (Friday), and taking it one day at a time," Dolphins head coach Mike McDaniel said. "The furthest thing from my mind is, you know, what is the timeline? We just need to evaluate and just worried about my teammate like the rest of the guys are. We’ll get more information (Friday), and then take it day by day from there."

Will Tua Tagovailoa retire?

In the immediate aftermath of his latest health scare, former NFL stars are encouraging the quarterback to hang up his cleats.

Pro Football Hall of Fame tight end Tony Gonzalez said "if I'm him, at this point, I'm seriously considering retiring from football."

"If that was my son, I would be like, 'It might be time.' This stuff is not what you want to play around with," Gonzalez added.

Former Dallas Cowboys wideout Dez Bryant had a similar message.

"That's it … NFL go ahead and do the right thing. Tua has had entirely way too many concussions. He need (sic) to retire for his longevity health concerns."

Tagovailoa, 26, is married with two children.

"The best thing I can do is not assess what this means from a football standpoint," McDaniel said.

How will injury impact Tua Tagovailoa's new contract, guaranteed money?

Taken fifth overall by the Dolphins in the 2020 NFL draft, he signed a four-year, $212.4 million contract extension this offseason. Of that, $167.1 million was guaranteed. But it's more complicated than that.

According to Spotrac, the new deal contained $93.17 million at signing. In March, another $54 million becomes fully guaranteed for his 2026 salary and is guaranteed for injury at signing.

Who is Dolphins backup QB Skylar Thompson?

A seventh-round draft choice in 2022, Thompson debuted against the New York Jets the week following Tagovailoa's concussion in Cincinnati. He started a pivotal Week 17 game that season and also was the team's starter for its wild-card matchup against the Bills during the 2022 postseason, which ended with a 34-31 defeat.

Thompson did not see the field last season. He completed 8 of 14 passes for 80 yards against Buffalo on Thursday night.

McDaniel said the team will move forward with Thompson at quarterback but will sign another signal-caller for depth.

"I'll tell you what, it makes me sick," Thompson said after the game regarding Tagovailoa's latest injury.

"Have a lot of love for Tua, built a great relationship with him," Thompson said. "And you care more about the person than the player – everybody in the organization would say the same thing."

Contributing: Tom Schad, Nate Davis, Tyler Dragon