In 5 years, one of Tom Brady, Peyton Manning, and Drew Brees will be the all-time leader in passing touchdowns. Currently, Manning is the passing touchdown king with 539 touchdowns, but will Brees or Brady catch him?

A year ago, I wrote about the fascinating touchdown race between Brady and Brees: at the end of the 2015 season, both had thrown 428 career touchdown passes. Last year, Brees threw 37 while Brady threw 28 in 12 games, so Brees is currently up 9 on Brady, 465-456.

But when I measured Brees and Brady last year, I measured them by calendar year. Both threw their first touchdown pass in 2001, so I thought a calendar year-by-year chart would be cool. But it probably makes more sense to compare the passers year-by-year by age, as I did yesterday with Brees and Manning for passing yards. That’s because Brees is about a year and a half younger than Brady (in turn, Brady is about a year and a third younger than Manning, but we haven’t compared them by calendar year).

So if we plot their passing touchdowns by age, Brees appears to have a huge leg up on Brady. That is, unless Brady plays until he’s 45:

Through age 31, Manning has an enormous edge on both players: he’s up 71 touchdowns on Brees, and 109 on Brady (2008, the year Brady missed, came during his age 31 season.

For their careers, Manning averaged 2.02 passing touchdowns per game, while Brees is at 1.996 and Brady at 1.92. For Brady, he and Manning both missed a season, but Brady didn’t throw any touchdown passes until he was 24 years old. Manning, meanwhile, had 52 through then (although it’s worth noting that Manning is “old” for his age-year, given that he was born in March, and Brady is “young” for his age-year, since he was born in August.) Given that Manning averages more touchdown passes per game *and* he started with a 52-TD head start, the odds of Brady catching him hinge entirely on Brady lasting a lot longer than Manning did. Brady is 83 touchdown passes behind Manning, and turns 40 years old in August. Manning, of course, never played a game in his 40s. Even if 40-year-old and 41-year-old Tom Brady are as good as in-his-prime Brady, the odds of him getting 83 touchdowns over the next two years are very long: Brady has only thrown 40+ touchdowns once in his career. So Brady would need 3 years of really good play — averaging 28 touchdown passes per year — to break the record. That seems pretty unlikely, too.

Brees, on the other hand, is in a different boat. He didn’t miss a season in his prime, like Brady or Manning. He did have a slower start, but that extra year really helped. Here is Manning’s lead over Brees in touchdown passes by age: he was up by 82 through age 28, though Brees chopped that down to +36 through age 34. At age 35 — the year Manning missed — Brees threw 33 touchdowns, bringing the margin down to just +3. Manning’s first two years in Denver helped bump that lead, tho:

The real question is how will Brees age. If he ages like Manning, he’s in trouble, since he’s already 26 touchdown passes behind Manning through age 37. Brees is also two months “older” than Manning by calendar year, since he was born in January. But even if Brees can defy age for a little bit longer, he’s no lock: he threw 69 touchdowns the last two years, and doing that over the next two years would still leave him needing to throw touchdown passes at age 40. Only two (Brady will almost certainly make three) have thrown 75+ touchdowns at age 40, and Manning showed us that the dropoff is usually pretty steep with older quarterbacks. I’d probably call this one a coin flip. What do you think?