"Baseball is a war of attrition and what's being attrited is pitcher's arms." - Billy Beane
Presented in the graphs below are the age distributions of the: (1) position players who had at least 250 plate appearances in 2009, (2) starting pitchers who tossed at least 90 innings in 2009, or (3) relief pitchers who tossed at least 40 innings in 2009. The blue dots indicate the average OPS+ or ERA+ for the players in the indicated age groups.
A passing glance reveals that the majority of hitters in 2009 were aged 25-29 and that there are many more position players in the major leagues beyond the age of 30 than there are those who are under the age of 25. There is some variation in hitting performance, though it is relatively insignificant and shows no age-dependent trend. The reason being that there is selection at work -- if a player isn’t performing to major league standards, he isn’t likely to accumulate 250 at-bats.
The plot for the 2009 relief pitchers exhibits a sharp increase in players up to a peak at age 27, and then a sharp step-down to pitchers aged 28-32, and then another step-down for pitchers who are 33 years or older. As with the hitters, the average ERA+ for the pitchers is consistent across all age brackets with a bit of an improvement for the pitchers over the age of 33. The numbers for the elder statesmen are buoyed by small sample sizes that include the likes of Mariano Rivera, Trevor Hoffman, Darren Oliver, and Takashi Saito.
The reason for this article is the graph above which shows the age distribution of starting pitchers in 2009. One-third of the starting pitchers were 25 or 26 years old. More than half of the starting pitchers were 26 years old or younger. There were 50 p ercent more starting pitchers aged 25 and less (53) than there were pitchers over the age of 30 (35). Two-thirds of the starting pitchers were in their 20s and three-fourths had yet to reach their 31st birthday.
Perhaps Oakland's general manager knows what he’s talking about. And with the passing of the steroid era, the trend appears to be pointing toward having still-younger pitchers. The median ages for starting pitchers in the last ten years: 2000-2004 = 28; 2005-2007 = 27; 2008-2009 = 26.
So what does this mean? For one thing, most of the pitchers in the rotations of major league teams were developed by said team’s minor league system. Only 30 percent of the starting pitchers in 2009 had accumulated the six years of service time required for them to become free agents. Fewer than 20 percent had ever been free agents. That means that four out of every five starting pitchers in 2009 were either developed by the team for whom they competed or were acquired via trade. Let that soak in for just a second -- 80 percent of an average team's starting pitching has to be developed or acquired in ways other than through free agency.
Combine that with the first compelling finding in this article (more than half of the starting pitchers in baseball are 26 years old or less), and you must come to the following conclusion -- organizations that can develop quality young pitchers are at a distinct advantage over organizations that cannot. Teams that want to contend on a yearly basis have to develop a pipeline of quality young pitchers who can compete effectively in the major leagues before they reach their late 20s. And that’s why the table and quote below should make you excited to be a fan of the Texas Rangers.
[Table description: Listed are the 2010 ages of 25 players in the Rangers' system who are being developed as starting pitchers.]
"The Rangers' system is down just a tad, as many top prospects had disappointing seasons, but a lack of positional prospects (especially at the upper levels) is more than offset by the most impressive collection of young arms in the game. The Rangers have just a ridiculous amount of young arms who are not 3/4/5 star prospects YET, but have to ability to turn into them." - Kevin Goldstein, 2010