At the end of September, the Panthers placed left tackle Michael Oher in the concussion protocol. He didn’t play again, missing the final 13 games of the 2016 season. On Friday, more concerning information regarding Oher’s health emerged.

Nearly six months later, Oher is still stuck in the protocol.

“He looks great, he sounds great, but he’s still in the protocol,” said general manager Dave Gettleman, per the team’s website. “He’s working out five days a week. He’s working his fanny off. He’s doing NFL workouts. He’s fully engaged in that weight room.”

Obviously, that’s concerning for non-football reasons. Oher isn’t the first NFL player to deal with a concussion for this long. As the San Diego Union-Tribune chronicled in January, former Broncos offensive lineman Sam Brenner suffered a concussion in the summer before the 2016 season. He ended up spending the entire year in the concussion protocol. He didn’t get cleared until January.

The Panthers’ report didn’t disclose what symptoms Oher is working through, but Brenner told the Union-Tribune about his struggles.

“I would have these mood swings,” Brenners said. “One second I’d be happy, the next I’d be depressed. My temper was very short. I would snap at (his girlfriend) about a lot of things that would seem minor.

“It made me irritable and unstable. Doctors passed along information, saying it really wasn’t me. It was the injury.”

Gettleman did say, however, that Oher’s workouts are rigorous.

“He’s doing NFL workouts. His workouts are not for the faint of heart,” Gettleman said. “That’s what I can tell you.”

Concussions, of course, have become an important topic of discussion in the NFL. It has also been a controversial subject. Some NFL owners, like Jerry Jones, have tried to refute the link between football and brain trauma. A year ago, The New York Times reported that the league’s research into concussions was flawed because it left out at least 100 concussions. Though the NFL gave concussion spotters the power to stop games before the 2015 season, the process has failed to work on multiple occasions. Back in November, Dr. James Andrews -- the renowned orthopedic surgeon -- told Sports Illustrated that if football were invented today, it would likely be outlawed due to its violent nature.

“It’s a collision sport,” Andrews said. “If we started a new sport today and we wrote up the rules and regulations and we called it football, they probably wouldn’t allow it. We’re all trying to do everything we can to make football safer, but that’s the way the sport is: There are always going to be injuries. We’re aware of that, and we’re all working to keep it that way. We want it to continue, believe me.”

Oher, 30, has been with the Panthers since the 2015 season. A first-round pick in 2009, Oher has played for the Ravens and Titans, too. He’s also known for “The Blind Side,” the book and movie based on his life.