The best NFL players at every age

Is Mahomes at 23 or Brady at 41 more impressive? (1:35)

Damien Woody and Mike Tannenbaum debate whether Patrick Mahomes' accomplishments at 23 are more impressive than Tom Brady's at 41. (1:35)

More than ever, football is a young man's sport -- a race against injuries, unwanted contracts and changing scheme trends. NFL rookies, in fact, were six months younger in 2019 than they were in 2002, according to league data. The best talent is typically, of course, the younger players.

That is, of course, unless you're a quarterback (or a certain ageless place-kicker).

Our ranking of the NFL's best players at each age level serves as a reminder that the league's best quarterbacks are also its oldest. The best defensive players are all under 29 years old. Here's the full accounting, which utilized Pro-Football-Reference.com and was based on how old a player will be on Dec. 31, 2019.

Note: Projections for the 2019 season are provided by ESPN's Mike Clay, and contract details are via Spotrac.

Age 21:
Nick Bosa, DE, San Francisco 49ers

Clay's 2019 projection: 47 tackles, 8 sacks
Signed through: 2023

We of course haven't seen most of the NFL's 21-year-olds on the field yet, but Bosa was the best position-neutral prospect in the 2019 draft class. Independent of any discussion about his decision to sit out most of last season at Ohio State, there is near-unanimous consensus that he will be a high-level pass-rusher as a rookie. He joins Dee Ford, acquired from the Chiefs, on a rebuilt Niners defensive line.

Runners-up: Jets defensive tackle Quinnen Williams, Steelers linebacker Devin Bush and Cardinals quarterback Kyler Murray all are in position to have strong rookie seasons.

Age 22:
Saquon Barkley, RB, New York Giants

Clay's 2019 projection: 2,060 scrimmage yards, 13 touchdowns
Signed through: 2022

After leading the NFL with 2,028 yards from scrimmage in 2018, Barkley will enter his second season in the MVP discussion. The Giants' decision to move on from wide receiver Odell Beckham Jr. and the looming quarterback transition from Eli Manning to Daniel Jones leave Barkley as the every-down anchor of their offense. He touched the ball 352 times last season. Is there any doubt he'll surpass 400 in 2019? (To answer the inevitable question: The NFL's post-merger record for touches in a 16-game season is 492, by the Buccaneers' James Wilder in 1984, as a 26-year-old.)