FOXBOROUGH, Mass. -- To ensure that 41-year-old quarterback Tom Brady doesn’t break down, the New England Patriots have a “broken-play” coach.

That might be oversimplifying things a bit, yet it does highlight one of the crucial storylines of Sunday’s season-opening game between the Patriots and visiting Houston Texans (CBS, 1 p.m. ET).

While all eyes will be on elusive Texans quarterback Deshaun Watson and how he moves around in his return from a torn ACL, it is Brady’s mobility – and his continued work with his legs and feet -- that is what many view as a key factor in achieving his goal of playing into his mid-40s.

Once an older quarterback becomes too stationary and shows an inability to evade the oncoming rush, things can fall off quickly. This is why, when Brady recapped the steps he took in the offseason to prepare himself for 2018, he said, “I’ve trained hard this offseason to improve my movement and anticipation.”

No one is mistaking Brady for a Clydesdale, which is the nickname given to him by wide receiver Julian Edelman, but coaches have taken notice.

“Certainly he’s made a big effort in the last so-many years to improve his ability to make plays outside the pocket and/or an extended play, whether it be in the field or in the red zone. I see the same thing [in 2018],” offensive coordinator Josh McDaniels said. “The ability to find people on the run. It doesn’t show up as much maybe in the preseason as it could in the regular season based on some of the things we may or may not be doing, in terms of game plan, but we’ve worked hard on it at practice.”

That’s also where the “broken-play coach” -- the role played by tight ends coach Nick Caley -- comes into play.

“He does a great job presenting that material to our group and talking about how we move when the quarterback moves [when a play breaks down],” McDaniels said of Caley, now in his fourth season with the Patriots. “I think our guys understand the play and how it works, and I think Tom has worked really hard to make those plays productive, because you never know when they’re going to come up.”

Caley further explained the role of the “broken-play coach.”

“We’re always trying to find ways to improve and be better, and there are a lot of teachable moments on tape that you gather from our experiences, and throughout football in general. You see opportunities, whether it’s scramble plays, or low-red zone scramble [10 yards and in], where you try to teach off those,” he said.

“Those are opportunities for us to improve a small element, but a big element at the same time. Those plays may come up one, two, three, four times a game, but when they do, it’s important everyone is on the same page and working the fundamentals to try to give ourselves the best chance.”

In addition, the Patriots have a standard drill during the individual portion of practice that gets Brady’s legs moving, as he is forced to scramble out of the pocket while reacting to the “rush” from an equipment staffer.

Is it possible that all the work at practice, coupled with his standard regimen at the TB12 Sports Therapy Center, has made Brady more nimble than he was?

“I never thought Tom was a very fast, athletic guy, but it looks like he’s actually moving faster, and his pocket presence is better than when I first came to the Patriots back in '03,” opined former New England safety Rodney Harrison, who is now an analyst for NBC’s "Sunday Night Football."

Texans head coach Bill O'Brien, who worked closely with Brady as New England's quarterbacks coach/offensive coordinator from 2009-11, sees it similarly.

"To me, I think he's actually improved [from that time]. He was able to do that," O'Brien said, laughing, as if nothing surprises him with Brady. "This guy is a great football player who works so hard at all the different parts of his game relative to mechanics and knowledge of the game and knowledge of his teammates. He's always working at it. I can remember when I was there -- phone calls in the offseason, always thinking about football and how to get the edge."

As Brady has crossed the threshold from the 30s to the 40s, part of that edge has been working more on movement and anticipation, and it shows.

“The first thing I look at with quarterbacks [possibly slowing down] is, ‘Are you still strong in the pocket? Do you go down easily? Are you shying away from contact?'" said Tony Dungy, the former head coach of the Buccaneers and Colts who now works as an NBC football analyst.

"I don’t see any of that with Tom. I still see him moving around in the pocket. I still see him willing to take a hit if he needs to deliver the ball.”