The Houston Texans won't be disciplined over their handling of quarterback Tom Savage's concussion, but the "unacceptable" incident has sparked changes to the NFL's concussion protocol.

The NFL and the NFL Players Association on Friday released a statement on their joint review of Savage's case.

He was allowed to play on in a game against San Francisco this month after a bone-jarring hit by 49ers defensive end Elvis Dumervil left him lying prone on the turf, his hands shaking involuntarily.

Savage was taken to the sideline medical tent for evaluation but returned to the field on the next Texans drive. A short time later he was re-evaluated, failed the concussion test and left the game.

"The NFL and NFLPA recognize that Mr. Savage's return to the game did not reflect the expected outcome of the Protocol," the joint statement from the NFL and NFLPA said.

"As such, the parties have agreed that no discipline will be assessed, but have already implemented several improvements to the Protocol to prevent such an unacceptable outcome in the future."

The review found that doctors weren't able to see the video that showed Savage's hands twitching until after he'd been cleared to return.

The new procedures announced on Friday include a pilot program that would have an independent neurotrauma consultant based at the NFL office to monitor broadcast feeds of all games.

The consultant will contact neurotrauma consultants and other medical staff on the sideline if they observe signs or symptoms warranting further evaluation.

The new rules define impact seizure, seen within seconds of a hit, and fencing responses -- a peculiar extended position of the arms that can follow concussion -- as immediate cause for a player to be removed from a game.

Any players who display stumbling, falling or any "gross or sustained vertical instability" must undergo a locker room concussion evaluation.

The league is also adding a third sideline neurotrauma consultant for playoff games and the Super Bowl to serve as a back-up if one of the original two consultants is busy attending to an already injured player.

The NFL has faced growing scrutiny in recent years over concussions and head trauma.

In 2015, the league agreed to a $1 billion settlement to resolve thousands of lawsuits by former players suffering from neurological problems.

Yet the issue has continued to loom large over the sport, with critics claiming the rules governing concussions are not enforced vigorously enough and that punishments against dangerous play resulting in concussions are insufficient.

On December 21, the Seattle Seahawks were fined $100,000 for failing to follow proper concussion protocol in allowing quarterback Russell Wilson to return to a November 9 game against the Arizona Cardinals after he had taken a blow to the head and neck in the third quarter.

Wilson briefly ducked into the sideline medical tent, but returned to the game before a medical exam was conducted.

The Seahawks became the first team to be fined for violating the protocol, which was immediately updated to instruct officials, teammates and coaching staff to take possibly injured players directly to a member of the medical team for a concussion assessment.