Philip Rivers calls it a blessing within his career. It's a blessing the NFL would like for many others too.

"I've never been diagnosed with a concussion," the San Diegan told the Union-Tribune recently as he nears his 12th NFL season as a starting quarterback.

Concussions and sub-concussions are brain injuries that are a threat to the short- and long-term health of players, and perhaps football itself.

Though the NFL has banned hits to the head that were legal decades ago, concussions are still part of the game. In recent years they've temporarily sidelined several quarterbacks, including Ben Roethlisberger and Aaron Rodgers.

Touchdowns are good for NFL revenues, and in addition to head-shot protection, the NFL game is far friendlier to quarterbacks than when Dan Fouts played for the Chargers. Nevertheless, two Buffalo Bills quarterbacks were concussed in a recent exhibition game.

Rivers goes into his warp-speed job with eyes wide open.

"I know that could happen on the first play of the next game. You could have a bad concussion," he said. "Could change the whole thing."

Rivers, who joined the Chargers in 2004, said he's sensitive to the topic of brain injuries and to reports that link football to the brain disease CTE.

He discussed his own good fortune only in response to the question of why he, a married father of eight children who has over $100 million in career earnings, is readying himself for another NFL season three months shy of his 36th birthday.

Don't construe his account as disrespectful to players who've endured concussion symptoms.

"But in all respect to them," Rivers said, "I have not personally dealt with any symptoms from a concussion, anything that makes me go, 'Gosh, is this worth risking?' Am I ruining this?' "

He said he's "very thankful" for a concussion-free career of some 200 NFL games, counting preseasons.

Pass-rushers have roughed up Rivers, who was a four-year starter at North Carolina State. They've slammed the 6-foot-5, 230-pounder to the turf, sometimes decking him before he could protect himself.

Even when defenders were warded off, the pocket wasn't always safe. During the 2013 season, for instance, Rivers was momentarily stunned when 350-pound teammate D.J. Fluker, in hot pursuit of an opponent, slammed into his face mask.

Rivers regrouped, and then led his team past the Eagles. Fluker was less fortunate in his four-year Chargers tenure, suffering no fewer than three concussions, all in practices. As a blocker, the 2013 first-round draftee was exposed to far more contact than Rivers.

Not immune to injury, Rivers sustained a knee-ligament tear that led to reconstructive surgery after the 2007 playoffs. He has played despite fractured ribs (per the public comment of teammate Antonio Gates) and a back injury that he said ailed him in the same 2015 season.

Yet, brain injuries are a category unto themselves, and brain doctors say there's still a lot to learn about them.

"I know every doctor will tell you there's a big difference between being diagnosed and having one," Rivers said of concussions. "So, I don't know. Could I have? Well, maybe. But I've never had symptoms to where I'm like, 'Gosh, this is crazy.'

"That's a real blessing."

Players are tempted not to report concussions symptoms, former Chargers safety Eric Weddle said a few years ago, out of a desire to keep their own jobs or to win a game. Weddle noted that concussed quarterback Alex Smith didn't regain his San Francisco 49ers job from Colin Kaepernick, who excelled after replacing a foggy Smith in that 2012 season.

Drew Brees said he kept a concussion secret when he was quarterbacking the 2004 Chargers. At the time his backup was Rivers, a first-round draft pick that year.

Roethlisberger has encouraged players to report concussion symptoms. Like Rivers a 2004 draftee, he told Steelers medical personnel during a 2015 game of issues with his peripheral vision. He was diagnosed with a concussion and didn't return.

"You can replace a lot of body parts," Roethlisberger told MMQB.com, "but you can't replace a brain. ... We are blessed to play this game but we also have a life to live."

The quarterback contemporary of Rivers who has raised the performance bar the highest is Tom Brady, who seven months ago led the New England Patriots to another Super Bowl victory.

Brady's wife, Gisele Bundchen, said her husband, who turned 40 this month, has had concussions "pretty much" and had a concussion last year. "We don't talk about it," she said earlier this year, "but he does have concussions."

Brady's agent said Brady wasn't diagnosed with a brain injury last year. Brady neither confirmed nor denied his wife's account.

"I don't really think that's anybody's business, what happened last year, and I'm focused on this year and improving and working on things I need to get better at," said Brady, who is to face Rivers' team this season and has said he plans to play until he's 45.

While some San Diegans may have concerns about Rivers taking hits as he moves deeper into his 30s, the quarterback said it isn't a topic he and his wife have discussed.

"We haven't even had a conversation to this extent about it. She's aware of it — the movie ('Concussion') that came out and all those things," Rivers said. "But, it's not something I think that gives her a great concern. I think, too, because it's not something I've really dealt with."

While respectful of the seriousness of brain injuries to football players, former Chargers center Nick Hardwick suggested outsiders should laud Rivers and other NFL players as competitors who are well-suited to the sport's aggressive nature. He wonders if the media sometimes overly fixates on the perils football players face.

Hardwick admires the competitiveness of players such as Rivers, a longtime friend.

Rivers said he's grateful for football and his ability to still play it.

The competition drives him, he said, as does a desire to rebound from last-place finishes in the past two years.

He said he gets a big kick out of teammates such as Gates, a colleague for his entire career. While there are exceptions such as current NFL players Jay Cutler and Marshawn Lynch, once a playing career ends, it usually ends for good, he noted.

"You can't just come back and do this," said Rivers, whose contract runs through 2019. "You can't come back and be around teammates and play with (Antonio) Gates. It's the people that make it what it is.

"And," he said, "I'm 35 years old. Shoot, I go to work. That's what we're built to do. I know it's work and it's play — but it's my job and I love doing it."