Breaking Down Production Over Time
There are a million ways to judge production, but only one gives us a one-number figure that compares across positions, seasons and even decades: Pro Football Reference's Approximate Value.
As explained in the series of posts that link takes you to, AV is one back-of-the-napkin number for a player's total production over a season, adjusted by their share of their team's production. These numbers aren't super precise, just a good rough guess of how productive and valuable a player was in any given season.
For each of the position groups, we can break down average AV for rookies, second-year players, third-year players and so on, giving us a picture of how players at certain positions tend to develop and decline.
Again, let's limit the sample player-seasons to 1978 and after, assuring apples-to-apples season lengths and similar offensive rules. The sets will be limited to players-seasons with at least 14 starts (and qualifying levels of attempts, the ones PFR uses for their rate stat minimums).
For some of the positions with the most variance, I've done the same analysis but with age, as well as years of NFL experience.
Quarterbacks
The quarterback is the most important, most protected position on the field, and it shows. The average starting quarterback plays about two seasons more than the average player at any other position.
Let's look at how quarterbacks develop and decline:
This dramatically shows the late start and slow development of quarterbacks. See how there are zero 22-year-old quarterbacks who've started 14 NFL games since 1978? From 23 to 24, 24 to 25 and 25 to 26, there was a massive leap in understanding with each generation.
At age 25, quarterbacks hit a long plateau; the number of them who start 14-plus games from age 25 to 30 is almost unchanged. The curve stays quite flat on the back end; quarterbacks good enough to be perennial starters have little trouble staying employed.
Is their performance that consistent? Let's check out their average Approximate Values:
There are a few very interesting things going on here. First, an across-the-board jump from year one to year two; quarterbacks who start both their rookie and sophomore seasons put up a significantly higher peak, average and low AV in their second season.
That low value continues to jump up and down around the number five for most of the rest of the chart; the weird dip in year five is due to an outlier, Ron Jaworski's 1978. He started every game, but produced an AV of only one; the next-lowest value for a fifth-year starter was four.
Peak AV climbs very steadily from year three to year eight; the best quarterbacks get steadily better, even as the average and low values stay flat.
At year 10, there's a significant drop-off in peak AV, then a steady decline to year 15. The average, however, begins to trend upward as the poorer starters stop playing. The elites aren't producing like elites anymore, but they're still very good and make up the majority of quarterbacks with careers that long.
At year 16, it dwindles down to just a handful of quarterbacks, so the peak drops sharply and the floor rises too. The last data point is just Favre being Favre.
What if we look at the same values, but broken down by age? Is there a magic age when quarterbacks get worse?
This chart is a lot more volatile.
The eye is drawn to the big dip in peak AV at age 29; this appears to just be a weird coincidence and not part of a larger trend (it's surrounded by very high AV values). Look at the jump from age 36 to age 37, though: High, average and low AV all take a big jump up—and then a huge dip. By 40, everyone but Favre is gone.
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Conclusion
There's no "age of doom" or "season of doom" for NFL players.
From one position to another, there are wildly different career development and production profiles. Even then, there are exceptions to every rule. One or two players at each position have broken all the rules and played at a high level into and beyond the high teens.
Across the board, though, we see that those players good enough to start for five years tend to play about 10 years, and even the best and hardiest lose an obvious step or two after 12 years.
Keep those facts in mind if you're a diehard fan in the market for a new jersey—or an NFL team with a key veteran going into a contract year.
