How The Game Has Changed: Part 1, Pitching

Since we’re so early into the season, it’s hard to write about many things that are currently happening due to sample sizes. As such, I’m going to take a step back and look at a few things that have changed over the past few years up to the past few decades and talk about how it applies to the game today.

For those of you that grew up watching baseball in the 80s, 90s, and maybe even before than, the game you see today is not going to be the same as what you grew up watching. This week, I’m going to take a look at pitching and it how it has changed since 1900. Next week, I’m going to take a look at hitters and fielding.

Starters are throwing less and relievers are more valuable than ever

You might have heard people talking about this in the offseason. I know a couple of posters here that brought it up, but the idea is simple: starting pitchers are throwing less and less and relievers are (obviously) throwing more. I’ll put it into graphical form for you:

Sean Testerman

As you can see, it’s a pretty steady decline, with starters throwing nearly 100% of the pitchers back around 1990 all the way down to nearly 60% in the 2010s.

As a result of this, relievers have become more valuable over time, having made a steady growth since the 1950s. However, the value of starting pitching did not decrease as one would expect. Rather, following the change (shrinking) of the strike zone in 1963 as well as lowering the height of the pitcher’s mound in 1969, the value of starting pitchers also rose rapidly:

Sean Testerman

As a result of these changes in the 60s, the MLB - which had been in its lowest run-scoring environment in decades - saw a massive surge in run scoring. This actually made pitchers more valuable than before as run suppression became much more difficult.

But if you were to look at this chart from this view, you might be inclined to think it has changed all that much in the last ~50 or so years. However, if we shorten that time to the last 18 years (since 2000), it paints a much different picture:

Sean Testerman

In the last 4 years, the percentage of innings thrown by starters has dropped from 66.48% in 2014 down to 61.93% last year. And so far through the short 2018 season, it’s dropped even further to 58.17%. And you can slowly see the SP fWAR slowly creep down and the RP creep up as a result.

And if you think about it, it makes sense. Pitching has turned into a game of strikeouts and pitchers are most likely to strike out batters the first time they face them (and subsequently less each time they face each other in a game). Teams have also gotten much smarter when it comes to matchups and have found it’s far more valuable to play matchups than to have one pitcher eat up multiple innings in a time (for the most part - see below).

I can go on about these changes but one thing is clear: it doesn’t seem like we’ll be reverting back anytime soon. The Rockies tried moving to a 4 man rotation a few years ago. The Rays are now moving to a 4 man rotation and a “bullpen day”. I can see other teams moving to this method sooner rather than later.

And we’re seeing it on the Diamondbacks, too, albeit in a different fashion. Relievers for the past few decades have predominantly been one-inning guys with a “closer” at the end. Now we’re seeing elite relievers that will go for 1-2 high leverage innings at a time before handing the game over to the “closer” in a lower leverage situation. Andrew Miller was instrumental in this revolution with the Indians, especially two years ago. We’ve seen it last year and this year with Archie Bradley. And there are other relievers like this, such as Wade Davis.

There is a theme here - these guys are largely converted starters. Let’s look at Archie for this example. In 141.2 IP as a starter in 2016, Archie Bradley put up 1.8 fWAR. In 73 IP as a reliever in 2017, Archie Bradley put up 2.1 fWAR. Archie was essentially twice as valuable to the team as a reliever, where he was able to throw harder and only rely on his two plus pitches. And he’s now turning into a borderline elite reliever.

So, keep this in mind for how the team shapes up over the next few years. We’re one of the few teams with 5 actually good starting pitchers, so we might end up being one of the laggards to change. But things could also change quickly, such as losing Corbin to free agency. We’ve got some talented arms rising in our minor league pipeline - will they be more valuable to us as starters or as relievers?