Tom Brady is set to enter the 2019 season as the quarterback of a New England Patriots team that is a heavy favorite to win the AFC East and one of the favorites to win the conference. Yes, that's right, the 42-year-old Brady is starting at the NFL's most important position on a team that is expected to do great things. 

According to four-time Pro Bowl quarterback Rich Gannon, the work Brady has put in to change his physical frame since entering the NFL is a big reason why he's still playing at such a high level. More importantly, Brady's plan can and should revolutionize how coaches go about training and conditioning their young quarterbacks.

"He says he wants to play until 45 and who am I to question that?" Gannon said at the 2019 CBS on NFL Media Day. "When you look at him physically, he looks like a much different player than when he came out. He's been on the cutting edge in terms of how he trains, things he does to recover after a performance. This sports science stuff is real and he's a great example of why strength and conditioning coaches are reconsidering how they go about training players."

Gannon signed with the Oakland Raiders in 1999 just prior to his age-34 season. He reinvented himself in Oakland and set career highs in completion percentage (67.6 percent), passing yards (4,689), and passer rating (97.2) during the 2002 season. Gannon would go on to win the 2002 regular-season MVP award and he helped the Raiders advance to Super Bowl XXXVI where they were defeated by the Tampa Bay Buccaneers.

What Gannon did was special, but the six-time Super Bowl quarterback is setting a new standard. Peyton Manning won a Super Bowl in his final season despite missing a large chunk of it due to injury, but he hadn't reached the age-40 marker yet. It's true, Brady has previously stated that he wants to keep playing until he's 45, and based on the work he has done to maintain his body, that doesn't seem unrealistic. 

His past and present teammates, those who have seen his training up close, agree. Earlier this offseason, former Patriots wide receiver Danny Amendola told reporters there is no timeline for Brady's retirement because he could "play forever" if he wanted to. Sure, the statement was laced in hyperbole, but the point Amendola is trying to make is that the training and sports science Brady has fully committed to gives him the kind of longevity that is new to anyone who has followed or played the game.

If you ask Brady, a regimen that he started in 2006 with his trainer Alex Guerrero is the key to his longevity. As he told Men's Health, the regimen begins at 5:30 a.m. and includes different brain exercises and muscle stretches to go along with his diet.

"I absolutely know 100 percent that it works, and the reality is I'm just a client who lives by the teachings," Brady said in the interview.

Of course, sports science and conditioning aren't the only reasons Brady is still playing at a high level. Gannon pinpointed two other key factors that keep him at the top of his game.

"One common theme with Brady is that he's been in the same system almost his entire career," Gannon said. "With Brady for example, you say he had Charlie Weiss, Bill O'Brien, Josh McDaniels, the voice in the headset may change, but the system never changes. Sports science is also a big part of it. They're taking care of themselves. Also, these guys are ultra-competitive. Their legacy is important. If I'm a younger player, those are the guys I'm studying."

During Gannon's resurgence with the Raiders, he worked with Gruden to develop a plan for managing his reps and keeping him fresh for the potential of a postseason.

"At some point, you have to listen to your body," Gannon said. "Quarterbacks want to take every rep, Peyton Manning was that way, but at some point, as a coach, you have to protect the player from himself. I know Jon Gruden did a great job of that late in my career, taking me out of certain situations. You have to make sure you get to the finish line."

Brady has taken less than a handful of days off -- known as maintenance days -- during training camp with the Patriots so far this summer. There are also small changes the Patriots have made to his workload. For example, Brady won't simulate the opponent's quarterback for the first-team defense -- that's backup quarterback Brian Hoyer's job. However, when he's not taking the day off, Brady typically takes every first-team rep in practice. This circles back to his competitive streak.

Brady's longevity goes beyond his conditioning, training, and practice plan. The veteran quarterback also does things during the game differently than other quarterbacks.

"He's taken good care about his legs, he doesn't take unnecessary hits, he gets rid of the ball quickly," Gannon said. "He's willing to throw it away and live for another down."

The Patriots have also made philosophical changes on the offensive side of the ball since Brady entered his 40s. During the second half of the 2018 regular season, the Patriots' offense began to shift to a run-first approach. In the postseason, rookie first-round running back Sony Michel averaged 112 rushing yards per game. From a personnel standpoint, the Patriots began mixing in more 12 and 21 personnel (featuring two tight ends on the field at once, and featuring a fullback, respectively). 

Michel totaled 280 rushing attempts, including the postseason. His 219 regular-season carries were the second-most from a single Patriots running back since the 2012 season. During the 2018 regular season, the Patriots ran the ball on 44.6 percent of their offensive snaps -- the second-highest frequency for them since the 2012 season (2016 was tops at 46 percent).

The Patriots are likely to reach or eclipse the 44 percent mark again in 2019. According to Gannon, this is likely all part of their plan. He believes the Patriots' play-calling mix had to change as Brady got older.

"Yeah it does, absolutely," Gannon said. "You look at quarterback movements, some of the things you may do on third down. You look at managing that quarterback position over a 16-game season and then how you put together a game plan and how you call a game. It has all changed."

The Patriots are still going to be the Patriots under Brady with Josh McDaniels as his offensive coordinator. You can still expect to see an offense that takes advantage of the best one-on-one matchup in the passing game over and over again. The Patriots will still burn teams with passes to their running backs and undersized wide receivers, who they somehow find a way to get matched up against linebackers and safeties. However, as Brady continues forward with this stage of his career, you can be sure the Patriots will be one step ahead of the game when it comes to how to best maximize his current skill set.

On the most recent episodes of HBO's "Hard Knocks" series, rookie Raiders safety Johnathan Abram was stunned to hear how old Brady was and made a note that the veteran quarterback was older than his father. Brady and the Patriots might make tweaks to their offensive philosophy in 2019, but they won't be reinventing the wheel. They know they can count on the 42-year-old to deliver in big moments, remain deadly accurate in the short passing game and red zone, and most importantly, process information faster than his any of his opponents. The latter trait doesn't get the publicity it probably should, but you can add it to the list of factors that allow Brady to continue being Brady as he enters the 20th season since the Patriots drafted him in the sixth round of the 2000 NFL Draft.