P.J. Williams of the Saints delivers a late hit on Kirk Cousins. (Jonathan Newton/The Washington Post)

As penalty flags flew, Washington Redskins left tackle Trent Williams was stunned to see quarterback Kirk Cousins jump to his feet after suffering a brutal, late hit while sliding at the end of a run — a blow that drew an unnecessary roughness penalty and cost New Orleans cornerback P.J. Williams a fine.

Later, in the third quarter of the eventual 34-31 overtime loss to the Saints in Week 11, Cousins was drilled again on a rush attempt — this time by Saints safety Vonn Bell, who launched himself at Cousins's head, while another defender shattered the lower right leg of lead blocker Chris Thompson, ending his season.

“I figured that first lick [from P.J. Williams] would have rung his bell pretty good, and the second lick [from Bell] looked pretty hard, too,” Trent Williams recalled when asked about Cousins’s resilience this season. “And that was just in one game.”

At 6-foot-3 and 202 pounds, Cousins hardly boasts the imposing presence of granite-sculpted quarterbacks Ben Roethlisberger or Cam Newton, each two inches taller and roughly 40 pounds heavier. But Cousins hasn’t missed a game since he was named the Redskins’ starting quarterback at the outset of the 2015 season.

Thursday night’s matchup at Dallas marks his 44th consecutive game.

Cousins has already been sacked more times in 2017 than in all of last season. (John McDonnell/The Washington Post)

Cousins’s durability has been particularly striking. Between his heightened determination to make plays with his legs, an injury-ravaged offensive line and some fierce opposing defenses, Cousins has been sacked 31 times through 11 games. That’s more sacks than he took all of last season (23) or in 2015 (26).

“The thing that has impressed me the most is that Kirk isn’t a guy who’s very big in stature, but he continues to put his body on the line, game in and game out, for his teammates and try to get wins,” said Williams, a five-time Pro Bowl left tackle charged with protecting Cousins’s blind side. “That’s what you want to see from a leader and a captain. And being that he’s under a one-year deal, that says a lot. There is a thing you call ‘making business decisions.’ A lot of people would probably go with the business aspect of that.”

A free agent at season’s end and projected to become the NFL’s highest-paid player in an overheated market for proven quarterbacks, Cousins hasn’t treated himself like a precious commodity. His zeal to make plays on critical downs, escaping the safety of the pocket and lowering a shoulder, if need be, not only has earned the respect of his teammates but has demonstrated to other teams — both opponents and would-be suitors — that he has guts, improvisational skill and the ability to withstand punishment.

Cousins will be unique when he hits the free agent market next spring, assuming the Redskins don’t bar him from leaving by using a third franchise tag at a prohibitive $34.5 million price tag. For $28.7 million, the Redskins could apply the NFL’s transition tag, but that means other teams could outbid them for his services, forcing the Redskins to match their price to keep him.

There is virtually no precedent for a healthy, established NFL quarterback hitting the free agent market while still in his prime. Barring catastrophic injury, Cousins should have five to eight years left in his career — longer, if he can replicate the longevity of future Hall of Famers Tom Brady, 40, and Drew Brees, 38.

Cousins’s achievements to date attest to his value. In nearly three seasons as a starter, he has thrown 73 touchdown passes to 29 interceptions, compiled a 99.7 quarterback rating and rushed for a dozen touchdowns. That alone puts him in elite company.

And he has made notable strides in intangibles in Year 3 as a starter. With less than optimum protection, he has kept his passer rating high. Eyed as interception-prone and overly cautious earlier in a still-young career, Cousins has completed some beautiful deep throws and off-script strikes this season.

Given Cousins’s track record and the scant supply of top-10 quarterbacks, former NFL front-office executive Joe Banner believes that even if he were injured, he still would command top dollar from teams willing to bank on his recovery.

“His next contract was always going to be huge,” Banner, a former president of the Philadelphia Eagles and chief executive of the Cleveland Browns, said in a telephone interview. “And even if he got hurt this year, it will still be huge.”

That’s because medical advances have shortened the timetable for athletes’ return from injury so markedly. “Teams are increasingly confident in the ability of doctors and trainers to project a player’s recovery and deliver on the fact that the player will return to what he was going to be,” Banner said.

Nonetheless, Cousins is doing everything in his power to guard against injury.

His resilience to date isn’t a matter of luck, though there has been an element of good fortune in it. It is more the result of a year-round training and recovery regimen that he has refined each season with help from his personal trainer, Joe Tofferi.

“It’s a true testament to his year-round preparation — the hours of stretching and training (both in season and out of season), his dedication is his sleep patterns, his very strict diet, and his faith,” Tofferi wrote in an email exchange.

An aspiring doctor before the demands of big-time college football forced him to change his pre-med major at Michigan State, Cousins approaches his training like a meticulously planned science project — fact-based and leaving nothing to chance. As Tofferi explains it, Cousins trains for all three planes of motion in his body: the sagittal plane (front to back movement), frontal plane (side to side motion) and transverse plane (rotational movement). The goal is to build strength, stability, power, endurance and mobility in each — all of which are taxed by the quarterback position.

His Redskins teammates have taken note.

“I tell you one thing: The guy is in tune with his body,” right tackle Morgan Moses said. “He knows every change that’s going on in his body. He spends a lot of time in the building and outside of the building rehabbing to make sure he’s ready for Sunday. We’re not perfect up front, and he gets hit sometimes. Sometimes they’re brutal hits. But when you got guys like that who are doing things outside the building to get ready, it allows you to play through things.”

That doesn’t mean Redskins linemen cheer everything Cousins does.

Williams, for one, challenged the quarterback about his refusal to slide — choosing to lower his shoulder and dive instead — on a 20-yard scramble against San Francisco that ultimately got him clobbered by safety Jimmie Ward.

“What are you doing, dropping your shoulder?” Williams asked on the sideline.

Cousins explained that he often feels more vulnerable to hard hits when sliding rather than courting collisions on his feet. By one count, on scrambles or designed runs, Cousins has been tackled or hit while diving 16 times, while he has slid just three times.

“That shoulder is worth about $200 million right now,” Williams warned Cousins on the sideline. “You don’t want to put that out there.”

That’s the “business aspect” of the equation Williams alluded to this week. Most franchise NFL players just months from free agency would protect themselves, eyeing the paycheck around the corner. Cousins is not, playing with grit in what may be his last season as a Redskin.

“He is the glue to his offense,” Williams said of Cousins. “So anytime he’s out there, this is a better team.”