From the hour you’re born you begin to die. – Simone de Beauvoir, “All Men Art Mortal”

From the minute a pitcher throws his first pitch in the major leagues, his velocity starts the long, slow path downhill. Seems dire, doesn’t it. Seems depressing, like sitting here wondering why your back, ankle, both knees, face and both elbows hurt after a relatively normal game of pickup ball.

But it’s true.

Check out the most recent work by Bill Petti and Jeff Zimmerman on the subject at FanGraphs. They ran pitcher ‘aging curves’ to see how different peripherals aged. The most difficult part of studying this phenomenon is avoiding selection bias — only the best pitchers survive to play another year, and therefore you have to do some math to make sure you aren’t just doing Roy Halladay and Jamie Moyer aging curves — but this pair of researchers has figured a way around it. And the results are stark. Pay particular attention to the long, black line that starts at zero and never returns, fading down away from where it once was.

It’s enough to make you put on some Smiths and curl up with a book and a glass of wine, or go to a dubstep show with no earplugs in, depending on how you deal with seeing your own mortality so starkly displayed. Pitchers stay within a half-mile of their peak velocity until they’re what age? 25? We keep moving that ‘young/not young’ needle further to the left.

Back to the greatest of distractions, fantasy baseball. How best to use this information to win your fantasy league?

Well, for one, there’s always the early-season talk about which starting pitchers lost the most velocity in the early going. This graph can help you perform a quick smell test. Mike Podhorzer tells us that Ryan Vogelsong (34 years old), CC Sabathia (31), Roy Halladay (35 next week), Tim Lincecum (27), and Brandon Beachy (25) are among this season’s biggest velocity decliners. Guess which ones you should worry about.

All is not lost for Roy Halladay — how could it be — on the other hand. When Jeff Zimmerman compared starters who maintained velocity over their careers to those that didn’t, he found that the maintainers pitched better later into their careers. Before heading south to about 90-91 MPH this year, Halladay sat at 92 for most of his career. Age comes for all of us, but Halladay may be able to stave it off longer.

What about the fact that velocities peak later in the season? Mike Fast, writing for Baseball Prospectus before he joined the Astros organization, found that fastball velocities peak in late July. The velocities you are looking at now might be anywhere from a half-MPH to a full-MPH lower in May then they are in July. That still leaves 30-somethings like Sabathia (-1.7 MPH), Vogelsong (-2.3 MPH), Josh Beckett (32 next week, -1.7 MPH) and Carl Pavano (36, -2.4 MPH) in a depressed state. They can cry on their bed made of money, but you might want to avoid depending on them in your keeper leagues.

There’s more to this. The Blue Jays famously have a reliever that lost velocity, lost strikeout punch, and then lost his role in the bullpen. It’s actually an old story that’s backed up by the numbers — relievers lose their ability to whiff batters quicker. They just age steeper in general. Look at starters on top of relievers, with respect to velocity and strikeout rate, thanks again to msrs Petti and Zimmerman:

Another way to say it is that once a reliever starts to see his velocity go, the rest of the package is about to go south with it. Once Francisco Cordero was sitting 93 MPH instead of 96, his swinging strike and strikeout rates struggled to remain average. Uh-oh Co-Co. What about other older relievers staring down the wrong end of the radar gun?

Among (qualified) relievers that got at least one save in 2011 and 2012, here are the top ten velocity decliners. Missing from the list is Heath Bell, who at 34 hasn’t thrown enough innings this season and ‘only’ lost .9 MPH off his fastball. Prominent on the list is a former Red Sox reliever that signed a huge contract, on the other hand.

Name Age FBv K% FIP- Velocity Decline
Bobby Parnell 27 94.8 25.0% 64 -2.4
Jeremy Affeldt 33 90.7 18.9% 70 -2.4
Jonathan Papelbon 31 93.3 28.3% 107 -1.7
Aroldis Chapman 24 96.4 46.3% 16 -1.5
Mitchell Boggs 28 93.7 28.6% 42 -1.5
Grant Balfour 34 91.4 17.5% 132 -1.4
Brandon League 29 95.2 14.5% 75 -1.3
Guillermo Mota 38 91.5 19.6% 134 -1.3
Joel Hanrahan 30 95.8 31.0% 149 -1.3
J.J. Putz 35 91.8 30.8% 126 -1.2

And for those that think that it’s not all about velocity, let me retort. Pitchers do, indeed, dig the radar gun. Mike Fast, this time for The Hardball Times, found that every MPH was worth a little bit more than 1/4 of a run allowed (RA not ERA). It’s useful.

Every pitcher is different. Notice that we haven’t talked about the 27-year-old Tim Lincecum, who has lost almost 4.5 MPH of fastball velocity since he entered the league, and 2.5 MPH since last year. He’s a bit young to be seeing this drastic loss, though. And even with a tick back, he’ll be aging faster than most pitchers. But he hit 93 MPH in his game last night, and maybe the changeup will still work for him at a reduced velocity. Johan Santana’s velocity is well down from his peak, and he’s still striking people out. In Lincecum’s defense, at least you can say he’s not yet 30. That’s more than you can say for this author.

But when you see the scouts lined up with their radar guns, or fans in the stands watching the stadium board for velocity, know that it’s for good reason. Because it’s likely that the number you see then will be, on average, better than any number you see again in the future. And that as the number gets smaller, so will that pitchers’ effectiveness decline. It’s natural. It’s aging.