The Strasburg Shutdown and What We Don’t Know

On Friday night, Stephen Strasburg took the mound in Nationals Park for the last time in 2012. Since I live about six hours from DC and I hadn’t seen him pitch in person yet, I figured I shouldn’t pass up on the opportunity to see him for myself, so I made the drive up on Friday afternoon. As you’ve undoubtedly heard, Strasburg wasn’t particularly sharp on Friday, getting removed after throwing just three innings, and so the Nationals decided that Friday was his final start of the year, moving his shutdown up one start and ending his season at 159 1/3 innings.

It’s obviously a rather controversial decision, and I’ve advocated for the position of more aggressive usage, skipping starts and manipulating the off days to try and make him available for the postseason. Watching him struggle in his final start didn’t disuade me from believing in the merits of that kind of approach, and I do think that perhaps there were alternative ways of handling his workload that might have allowed him for pitch deeper into the season. However, the unavoidable reality of this situation is that everyone is dealing with a great quantity of unknown variables, and for any of us to say that one decision is distinctly better or worse than another is probably an on overestimation of our own knowledge.

The secret to keeping pitchers healthy is still perhaps the biggest unknown entity in baseball, and our ability to predict which pitchers are going to stay healthy is not much better than simple dart-throwing. As more focus has shifted to the causes of physical breakdown, workload has gotten more than its fair share of attention, and efforts to avoid overuse have become far more commonplace in the last 10 to 15 years. However, even with this focus on responsible workloads, we haven’t seen a sea change in how often pitchers are getting hurt.

Given that pitchers have different physical strengths and weaknesses, it’s likely that a one-size-fits-all approach isn’t all that useful, and what might be good for one pitcher could be bad for another. So, while we can say with some certainty that Strasburg would have been at a higher risk of injury if he would have thrown 250 innings this year rather than the 160 he actually threw, we don’t really know where he lies on the reasonable usage spectrum. You could probably make a case for any number between 160 and 250 and have a reasonable amount of evidence on your side that the total innings count wouldn’t be significantly more harmful than any other number in that spectrum. And, with a knowledge gap that large, it’s just hard to have any kind of strong opinion about what the right number for Strasburg this season actually was.

The Nationals obviously erred on the side of caution, giving their ace a number pretty close to the lower bound, and refusing to shift his starts around to maximize the leverage of those innings. They wanted to allow him to maintain his regular patterns, and again, this is an area where we simply don’t know the effects of alternative options. There just isn’t much historical precedence for this kind of situation, and the uniqueness of each pitcher’s body limits what we could learn from earlier cases anyway.

So, the Nationals chose something like the most conservative usage path possible, but given how little is known about keeping pitchers healthy, their decision is certainly within the bounds of what one could consider reasonable. And, of course, health isn’t the only variable in play here.

As we saw on Friday night, there is some evidence that Strasburg is currently somewhat less effective than he was earlier in the season, and perhaps a full season of pitching is starting to catch up with him to some degree. For instance, take a look at his PITCHF/x velocity chart:

While he has mostly maintained his average velocity throughout the summer, his peak velocity is down from earlier in the season. In May and early June, he was regularly getting up into the 98-99 range, but lately, he’s topped out at 96 or 97. It’s not a smoking gun, but given that velocity tends to increase as the season goes on, the fact that Strasburg’s fastest pitches have gotten a little bit slower suggest that there is some legitimacy to the idea that he’s beginning to wear down.

There’s also some evidence of declining dominance in opposing batters swinging strike rates. In his first start of the season through July 15th — his first 18 outings — opposing batters only posted a swinging strike rate below 9% twice, and they were over 13% seven times. In his last 10 starts, however, he only posted a swinging strike rate over 9% five times, and only once got over 13%. His command also wasn’t as crisp as it was earlier in the year, as he walked three or more batters in a game four times in his last 10 starts after doing it four times in his first 18 starts.

Early season Strasburg was the most dominant pitcher in baseball, at least on a per-innings basis. Recent Strasburg has been more human, mixing in some good starts with some clunkers. If this trend was going to continue, it’s certainly possible that the gap between Strasburg and Ross Detwiler in October wouldn’t be so large that swapping them would result in a huge change in expected outcomes. In fact, you could argue that the outcome differences now aren’t even that large.

Strasburg’s posted a 2.82 xFIP this year, just about 1.50 runs per nine innings better than Detwiler this season. Strasburg’s posted higher than average BABIP and HR/FB rates, while Detwiler has been below average at both, so you might want to adjust that gap down slightly to account for the fact that there might be some difference in skills in those FDP areas. So, maybe the gap is 1.25 runs per nine innings instead. That’s certainly a big difference, but we also have to remember that October baseball is not the same as regular season baseball, and that managers can be much more aggressive in their bullpen usage in the playoffs. Given how deep Washington’s relief corps is, it’s unlikely that either pitcher would be asked to go beyond six innings, and five is probably more likely against a good offensive opponent. So, instead of 1.25 runs, we’re probably dealing with something closer to 0.7 runs per start difference.

And that’s using Strasburg’s full season line. If you think he’s wearing down, maybe he’s more of a 3.25 xFIP guy going forward, and that would push the difference more towards 0.5 runs per start. Don’t be fooled by those “ERA since the All-Star break” graphics that say that there’s no drop-off here, but a half run gap isn’t overwhelming, especially if you think that the trade-off is getting a healthier Strasburg for the future.

And then, of course, there’s the significant variance around player performance in small samples to begin with, and we’re not just talking Strasburg and Detwiler here. There’s a real chance that the playoff games that Strasburg would have pitched in wouldn’t have been close enough to be decided by the quality of the starting pitcher anyway. If we built a histogram of the potential outcomes of any Strasburg playoff start, there would be a tail on one end that represented a blowout by the Nationals, in which they could probably roll out any pitcher they wanted and still win the game. Likewise, there would be a tail on the opposite side of the spectrum that represented a dominating performance from the opposing starter so that even a great performance by Strasburg would still result in a loss.

The starting pitcher is an important factor in the end result of a ballgame, but it isn’t the deciding factor, and it’s certainly possible that the decision to use Detwiler instead of Strasburg ends up not having much of an effect on the Nationals playoff chase at all, simply due to outcomes that have nothing to do with the quality of each pitcher. Combine that with the volatility of projecting Strasburg going forward, the huge unknown that is pitcher injuries and reasonable workloads, and the fact that the Nationals do have a good team even when Strasburg’s not on the mound, this decision by the Nationals is certainly defendable.

It’s not the only defendable decision that they could have made, but this is an area where it just doesn’t make much sense to take a strong stance one way or another. There are so many unknowns that the best thing we can do is admit that we don’t know enough to have a strong opinion either way. The Nationals are doing what they think is in their franchises best interests, and they very well may be right. They may also be missing a chance to take a deep playoff run, and the reward that comes from that kind of run might be worth the extra risk. There are a lot of maybes here. When there are this many questions that we just don’t have the answers to, the best thing we can do is acknowledge where our limits are. On handling Stephen Strasburg, we just don’t know enough to say whether any one decision is better than another. The Nationals made a decision and stuck with it. That’s probably all they could have done.