Tom Brady is poised for another gruelling duel against Father Time as the 2018 NFL season kicks off on Thursday with the league's elder statesmen looking over their shoulders at a new generation of quarterbacks.
After years of wondering where and when the natural successors to the likes of Brady, Ben Roethlisberger and Drew Brees would emerge, the NFL now appears to be blessed with a rich seam of talent at its most coveted position.
Last season, at least, there was little indication that the old guard were ready to shuffle off into the sunset.
New England star Brady will head into a remarkable 19th campaign at the age of 41 as the reigning NFL MVP, having led the Patriots into the eighth Super Bowl of his career.
Brady's age-defying statistics -- his 4,577 passing yards were the fourth highest total of his career -- were mirrored by similar standout seasons from his evergreen contemporaries.
Four of the top five passers in 2017 are now 36 or older. New Orleans Saints veteran Brees will start the new campaign at age 39, while Pittsburgh Steelers signal-caller Roethlisberger and San Diego's Philip Rivers are both 36.
Brady and Brees could both pass significant milestones this year if they are able to reproduce their 2017 form.
Brady needs only 21 touchdown passes to surpass Peyton Manning's haul of 579, the most touchdown passes in league history.
Brees could also supplant Manning's all-time mark for passing yards if he adds another 1,496 yards to his total.
Brady, whose relationship with Patriots coach Bill Belichick has been the subject of intense speculation during the off-season, insists his competitive spirit remains undiminished.
"I really enjoy the competition," Brady said. "I've always thought the approach was being my very best. My motivation comes from not letting my teammates down.
"I know how much people put into it — our coaches, teammates — to have a successful season. We work year-round for it. I don't want to be the reason for why we aren't successful."
- Changing of guard? -
Yet could 2018 mark a changing of the guard? There are plenty of contenders who look well-positioned to challenge the established hierarchy.
The Philadelphia Eagles will open their season against the Atlanta Falcons on Thursday with Nick Foles at quarterback, but have 25-year-old Carson Wentz poised to return to fitness following the knee injury which curtailed his dazzling 2017 campaign.
The Los Angeles Rams meanwhile, who have strengthened during the close season, will be looking for another big year from their 23-year-old quarterback Jared Goff, the 2016 number one draft pick.
While Wentz and Goff are obvious contenders, players like Chicago's Mitch Trubisky (24), Houston's DeShaun Watson (22) and Kansas City's Patrick Mahomes (22) could also come into the mix.
Jimmy Garoppolo, Brady's long-time understudy at the Patriots, is also expected to be a pivotal figure in his first full season with the San Francisco 49ers.
The NFL's quarterback depth will also be enhanced by the return from injury of the Green Bay Packers' Aaron Rodgers and the Indianapolis Colts' Andrew Luck.
Luck missed the entirety of the 2017 season with a shoulder injury but insists he is fully recovered as he hopes to start delivering on the promise that saw him picked first in the 2012 draft.
Rodgers, meanwhile, regarded by many commentators as the best quarterback in the NFL, starts the new season on a high after agreeing a new $134 million contract.
The 34-year-old two-time NFL MVP missed most of last season after suffering a shoulder injury in week six as the Packers failed to reach the playoffs.