Pitch Velocity and Aging Curves

On numerous occasions I have railed with the training regimens imposed on young arms by today's youth baseball leagues, primarily because it has led to an exponential increase in arm injuries (""). That said, it has also led to an increase in the number of pitchers who can throw exceptionally hard. Pitchers who threw 100 mph used to be rare. Now, they're becoming more and more common. As an article in the Washington Post ("Velocity is strangling baseball — and its grip keeps tightening") recently noted:

Im 2008, there were 196 pitches thrown at 100 mph or higher... In 2018, there were 1,320, a nearly sevenfold increase. In 2008, only 11 pitchers averaged 95 mph or higher; in 2018, 74 did. Aroldis Chapman of the New York Yankees and Jordan Hicks of the St. Louis Cardinals have both been clocked at 105 mph.

Average pitch velocity has also increased. Not at quite the rate of 100 mph pitches and pitchers, but,  as the graph below from 538 illustrates ("Where Have All The Crafty Pitchers Gone?"), the increase has been steady and substantial for the last several seasons.

Unsurprisingly, this increase has led to a decrease in batting averages and a rise in the number of strikeouts. In fact, 2018 marked the first time in the history of major league baseball that there were more strikeouts per game than hits.

Not only is this decline in offensive production because pitchers are throwing harder, but also because teams are using more pitchers each game. It is rare for a starter to finish a game. There is too much evidence that shows that a starting pitcher's effectiveness decreases the third time through the batting order. Thus, teams are increasingly using relievers, most of whom are only expected to pitch an inning or less, which means that they can throw as hard as they want without worrying about having to pace themselves. Thus, while in the past, in later innings batters could "look forward" to a pitcher's whose velocity had fallen from the start of the game and they had already seen at least twice, now they have to face a fresh (and unseen) arm.

What I'm curious about is the effect that the increase in pitch velocity, if it remains unchecked, will have on the aging curves of position players. What's an aging curve? An aging curve measures the average improvement or decline expected based on a player’s age. Here's a brief description from FanGraphs ("The Beginner’s Guide To Aging Curves"):

Human beings generally can’t run as fast at 36 as they can at 26. They get injured and tired more easily. Sometimes their vision or hand-eye coordination diminishes. No two players bodies age in exactly the same way, but overall there are consistent trends, [but]... players are typically much better overall at 27 then they are at 37.

The graph below plots expected or average runs above average (RAA) by player age. As it indicates, an average player peaks in terms of run production around the 26 years old, and at around 30-32 years old, their productivity drops below that of an average 21 year old. Better players tend to age slower or at least are still productive into their early 30s, but what this graph (and corresponding data) suggests is that when a player reaches 30, it is probably time to start looking for a replacement.

So, what might the increase in pitch velocity have on aging curves? Well, it's not hard to imagine that having to hit a high-90 to low-100mph fastball becomes increasingly difficult as reaction time diminishes. Thus, I wouldn't be surprised that the long term effect could be to push the curve to the left. That is, players might peak at a younger age or their decline could occur more rapidly.

The decrease in offense has corresponded with a decline in attendance. People may lament the steroid era, but it brought people out to the ball park. Not any more. Attendance has declined for six straight seasons. In 2018, average attendance was 28,659 per game, which is 13 percent from its 2007 peak. Thus, it is no surprise major league baseball (MLB) is looking into ways to address the issue. Back in 1968 when batting averages hit an all-time low, the MLB lowered the mound 5 inches (from 15 to 10) and reduced the strike zone. Now, they are talking about moving the mound back. The last time MLB moved the mound back was in 1893. Back then, they moved it back 10 feet, and batting averages jumped 35 points and strikeouts dropped by 34 percent. I don't anticipate anything quite so drastic. In fact, beginning in the second half of the 2020 Atlantic League season, the mound will be moved back by two feet. It will be interesting to see its effects.