Where have Jesse Hahn's strikeouts gone?

Let us begin with some good news: Jesse Hahn is starting for the Oakland A's tonight. He was dealing in his last start on April 18, but he had to leave early due to a blister on his finger. He missed his next start while it healed, but now he's ready to give it another go. That pushes Jesse Chavez back to Thursday in the series finale, and Scott Kazmir to Friday in the opener in Texas.

Hahn is off to a good start so far, with solid showings in each outing. He tossed a six-inning, three-run quality start in his debut, he carried a no-hitter into the sixth against Seattle, and he had a shutout going against the Royals with a low pitch count in the sixth inning before the blister got him. That's a resume filled with equal parts success and growing pains, but it has added up to a 2.12 ERA in 17 frames. His performance is not a surprise, since he was excellent last year in a handful of starts for the Padres.

While his success hasn't been a surprise, though, the way he has achieved it has been. Last year, he mostly used a three-pitch arsenal of fourseam-sinker-curve, balanced evenly between the three, with a few changeups mixed in. He used that repertoire to strike out about a batter per inning while keeping half his batted balls on the ground -- an excellent profile for a pitcher to have, though his walks were a bit high. This year, though, the groundballs remain while the strikeouts and walks have utterly vanished.

Hahn, 2014: 8.6 K/9, 3.9 BB/9 (22.9 K%, 10.5 BB%)
Hahn, 2015: 2.6 K/9, 1.6 BB/9 (7.5 K%, 4.5 BB%)

In raw totals, he's thrown 17 innings and recorded five strikeouts and three walks. Beyond the normal small-sample caveat, it must also be noted that his three starts came against the Royals (last in MLB in Ks), Mariners (21st) and Rangers (T-20th). He has only faced teams that don't strike out much, and they mostly don't walk much either. That might be the answer to the question in the headline right there: he just hasn't faced the Astros and Rays and Yankees yet.

When I went looking for Hahn's stats today, I noticed that Eno Sarris on Fangraphs already beat me to this topic. It's not a long post but it packs a lot of punch and it includes a lot of quotes from Hahn himself; I recommend you check it out. The crux of the article is that Hahn has switched up his pitch selection to feature different offerings and altered his approach to induce different results, with neither thing necessarily needing to be a permanent change. Sarris highlights the increased usage of Hahn's changeup, and Hahn echoes that observation:

"It's early in the year," [Hahn] said. "I'm happy to get more grounders and quick outs with my two-seamer and changeup now, and once I start seeing these guys more often, I'll switch it up and we'll see more strikeouts."

That makes total sense. I love strikeouts from my pitchers, but they aren't everything; I love wins and outs more than I love strikeouts, in that order. If he can routinely carry shutouts into the sixth inning with his contact-oriented approach, I'll take that for now. He has all year to learn to consistently extend deeper into the game with his strikeout stuff.

*** Read Eno Sarris' post on Fangraphs, read it, it'll make this article make more sense, just do it, it's short and user-friendly and interesting***

There's only one problem, though. The numbers don't add up. He's not throwing his sinker more, he's throwing it half as often as he used to. He is throwing his changeup more, but the jump is only from around 8% to 13% -- not a major increase, and still not enough for it to even crack his top-three most-used pitches. His curve has only seen a small downtick, about equal to the upswing in changeups. And now he's throwing his four-seam fastball nearly half the time, instead of around 30%. To top it off, he's throwing everything about 2 mph harder than last year, which seems like something you do when you want to miss more bats.

This is why I'm confused. Everything in Sarris' article makes total sense and was exactly what I was expecting to find when I went looking. Hahn is pitching to more contact, and he even says so himself. But the numbers tell a different story, and I just don't know who to believe. On one hand, no one knows better than the player himself. On the other hand, numbers don't really lie, at least not in this way. For now I'll just chalk this one up to small-sample oddity, and offer three possible results (though many others exist):

1. Hahn continues throwing lots of four-seamers and curves, and his Ks come back.
2. Hahn's Ks stay low, but the usage rates of his pitches catch up with the narrative and it becomes clear that he truly is throwing more sinkers and changeups to induce more contact.
3. It all keeps going like this, with his strikeout stuff resulting in rivers of ground balls, and we all realize that we know nothing at all about baseball, not a darn thing, because it's just a random number generator and nothing is guaranteed and there is an exception to every rule and all of your predictions are pointless.

I honestly don't know which one to pick. However, like I said before, my instinct is to take the player's word for it until I have an excellent reason not to, and right now I only have a faint reason not to believe him. I'll guess that he really is trying to feature those contact pitches more, and that maybe his strikeout rate will settle in around 6-7 per nine innings instead of 8-9.

Is that a good thing or a bad thing? Well, obviously that depends on whether it works for him or not; if the contact isn't turning into grounders or the grounders aren't turning into outs, then he should go back to trying to rack up strikeouts. But as an overall concept, there is nothing wrong with giving away Ks in the quest for more total outs. In fact, Hahn isn't even the only guy on his own team who is doing it. Sonny Gray has dropped all the way down to 6.2 K/9 this year, and his usage rates really do support that conscious strategy -- he's throwing more sinkers at the expense of his heater and his curve, exactly as Hahn says he's doing. It's certainly working for Sonny, as he's sporting a 1.98 ERA and a career-low walk rate and is routinely pitching into the eighth inning. That doesn't mean it will work for Hahn too, but considering how similar their styles and repertoires seem to be I think it's absolutely worth trying.

Jesse Hahn isn't striking out as many batters, and he's almost certainly doing it on purpose. The usage rate numbers may not have caught up yet for some reason, but the results sure have. Interestingly, just as the A's move to a more contact-oriented approach on offense in what I assume is an effort to make things happen via increased quantity of batted balls (and the inherent randomness they bring), their pitchers seem to be forcing that strategy on their opponents simultaneously. Perhaps these particular pitchers are good enough at inducing weak contact that it's comparing apples and oranges, but I would think that a team who values one thing would want to attack its opponent by withholding that one thing (like the Royals and their strikeout-heavy bullpen). It's a bold strategy, Cotton. Let's see how it works out for them.