The National Football League Players Association terminated the independent doctor who cleared Miami Dolphins quarterback Tua Tagovailoa to return and play on Thursday after sustaining an apparent head injury.

NFL: SEP 25 Bills at Dolphins

Tua Tagovailoa walked off the field after a play.

Icon Sportswire via Getty Images

The doctor was fired by the union as a result of its investigation into the incident.

Tagovailoa, one of the sport's bright young stars, stumbled during Miami's game against the Buffalo Bills after hitting his head against the ground, but returned to action and played in the team's Thursday night game against the Cincinnati Bengals.

Sources told the Athletic that the consulting doctor made a number of mistakes in evaluating Tagovailoa.

Tagovailoa was carted off the field in the second quarter of the Bills game after he suffered a gruesome head and neck injury.

In his first statement on the situation Friday, Tagovailoa said he was feeling better and grateful for the support and care he had received.

The league's chief medical officer defended the league's handling of Tagovailoa in an interview with the league's network.

PLAY 1/1 Skip Ad Continue watching after the ad Loading PodsVisit Advertiser websiteGO TO PAGE

The Dolphins stood by their actions, and their head coach Mike McDaniel said after Thursday's game that Tagovailoa did not suffer a concussion. One of the league's unaffiliated neurotrauma consultants, who are on the sideline of every game providing a third-party evaluation of any potential head injuries and have the power to remove players from games for evaluations, was fired. The treatment of traumatic brain injuries in the National Football League has been criticized and the league agreed to pay a $765 million settlement to thousands of former players. Boston University researchers found evidence of the brain disease chronic traumatic encephalopathy in 99% of the brains of former National Football League players. Depression, suicidal thoughts, and issues with impulse control are some of the symptoms of the disease. Critics wondered if the ethics of playing football were affected by the link with chronic traumatic encephalopathy.

Chief Critic

Tagovailoa should not have been allowed to play, according to the president of the players' union. DeMaurice Smith said the union would seek every legal option.

Surprising Fact

This is the third high-profile controversy involving the Dolphins this year, its former head coach Brian Flores sued the NFL in February for racial discrimination, also alleges the team's billionaire owner Stephen Ross offered him money to purposely lose games, and the league suspended and fined Ross in August and docked

N.F.L.'s concussion protocol is under scrutiny after Tagovailoa was hit hard again.

In football, what to know about C.T.E.