The Angels are, apparently, committed to trying a six-man rotation. This is interesting, but as FanGraphs pointed out, also problematic because of the strain it puts on the roster. I would add that pitchers tend to get hurt, after all, and most teams have a hard time filling a five man rotation. So a six man rotation is going to be even harder even without the roster crunch.
One of the things that gets lost from time to time is that we still have no idea how to prevent pitcher injuries. There are numerous write ups and studies with no evidence that anything makes a huge difference except that there is a correlation between extreme fatigue and injury. And by extreme fatigue I’m referring to games in which pitchers throw a huge number of pitches or a lot of pitches in stressful situations.
But even that isn’t a great predictor. Indeed, the best way to predict whether or not a pitcher will get hurt is by looking at whether or not he’s been hurt before. And so it may be that these kinds of things aren’t predictable. Some pitchers will get hurt and others won’t and that’s just all there is to it.
So what if a team like the Reds went back to the 4-man rotation? The odds of having any 4 pitchers healthy at once are better than the odds of having any 5 pitchers healthy at once. Given how in-game pitcher usage is changing, the kind of damaging stress that can occur from throwing too many pitches without recovery time is getting very low.
If the Reds were to try it, they would have an Opening Day rotation of (probably): Luis Castillo, Anthony DeSclafani, Homer Bailey, and Brandon Finnegan. They would then have a AAA rotation of Tyler Mahle, Amir Garrett, Sal Romano, and Robert Stephenson, any of whom could come in should one of the big leaguers get injured. That’s two full rotations of major league-caliber starters. And we haven’t discussed Michael Lorenzen or Cody Reed.
The idea here, essentially, is that it makes no sense to think of a rotation as containing a set number of pitchers. Rather, we should view it as a set number of slots. If you get the slots down to the smallest reasonable number, then you should be able to maximize the innings you get from your most durable starters, and thus reduce uncertainty.
Think of it this way: There are almost certainly major league pitchers available who can pitch 250 innings. But the way the modern game is set up, it’s almost impossible to reach that number. In a theoretical universe, a team’s top-8 starters might situate like this in terms of their carrying capacity for innings:
250, 250, 180, 150, 125, 100, 100, 50
It is the job of management to maximize the innings they get from their best pitchers. Also, the best pitchers are not always those who throw the most innings. So let’s imagine that the quality of those pitchers goes something like this:
Who do you want in your rotation? You’re almost certainly going to need all 250 innings from pitchers 4 and 6 and you can cobble together another 500 or so from pitchers 1, 2, 3, and 5. You’ve got 7 and 8 hanging out in case you need them, but in a 4-man rotation you probably don’t because pitchers 4 and 6 are eating so many innings, it’s possible to use the other pitchers to compensate for each other. Effectively, the idea behind a 4-man rotation is that it raises your floor without lowering your ceiling much at all.
This is a moderately disorganized post and I’m still figuring out what I think about it, but given that nothing that has been tried has been shown to reduce the frequency of pitching injuries, it makes more sense to maximize the innings you get from pitchers who are physically capable of being workhorses while filling the remaining holes with those pitchers who are more fragile.
Now, let’s look at the Reds top-8 in terms of innings pitched last year. Except for Stephenson, where we’ll use 2016 since he was a reliever for part of last year. Major league and minor league innings are included.
- Luis Castillo – 169.2
- Anthony DeSclafani – 6.2
- Homer Bailey – 101.2
- Brandon Finnegan – 13.0
- Sal Romano – 136.1
- Robert Stephenson – 163.2
- Tyler Mahle – 164.1
- Amir Garrett – 137.2
Now, given artificial innings limits, it seems the three pitchers most likely to be able to handle a full season of starting are Castillo, Stephenson, and Mahle. In the next tier you probably have Amir and Homer. Amir because his injury wasn’t an arm injury and Homer because he seems to finally have healed. Next is Romano, and finally Disco and Finnegan – who have to be considered very high injury risks for now.
Now, I don’t know what kind of rotation you cobble together from that, but I do know that a four-man rotation gives you a lot more options. I’m interested to hear what you folks think in the comments.