Alex Chamberlain analyzes Dallas Keuchel's five most recent starts, in which Keuchel looks like an ace if one digs beneath the surface.

Can He Return To Form?

I won't say Dallas Keuchel is out of the woods just yet. I think it might be a bit of a hyperbolic characterization of his recent success. Even the word "success" is a bit hyperbolic here, but take note: in Keuchel's last five starts, he has struck out 34 hitters and walked only four (9.8 K/9, 8.5 K/BB) while inducing ground balls at a vintage Keuchelian 63.3% clip.

Except he hasn't looked like vintage Keuchel in terms of outcomes. His baserunner prevention and ground ball tendencies have been good for a 2.42 xFIP since May 22, and his 2.78 xFIP in the last 30 days ranks ninth among all qualified starters. But an ugly batting average on balls in play (.337 BABIP), strand rate (53.9% LOB) and home run rate (23.5% HR/FB) elevated his ERA to 5.74 during this peripherally excellent stretch. It's a tale of bad luck and bad choices.

Because, as Twitterer Ryan Brock noted, Keuchel still allowed a discouraging number of hard hits. It's kind of like the Michael Pineda dilemma, in which Pineda demonstrates excellent baserunner prevention skills but, for no better way of describing it, is simply too hittable.

How Keuchel Is Fixing Himself

Enter the slider. In his last five starts, Keuchel has ramped up his slider usage from 21.5% to 33.7%. That's great, because the slider is arguably his best pitch. In 2015, the slider allowed an anemic .106/.147/.181 against. The slider hasn't been quite as good this year -- .165/.195/.266 -- but it's still really, really good. In his last five starts, it has induced ground balls at a 61.4% rate and hasn't allowed a single extra-base hit.

Within the most recent hyperlink also lies the issue inherent to Keuchel's prolonged struggles. His go-to pitch, the sinker, has allowed at least one extra-base hit in 10 of his 14 starts. To return to Ryan's point: if we're using isolated power (ISO) as a proxy for hard hits, then Keuchel's slider is incredibly effective, while his sinker is incredibly problematic. And Keuchel continues to, well, go to his go-to, throwing it almost 50% of the time, despite the increased slider usage. Compare his sinker usage from his first eight starts to his latest five -- it's almost identical.

There seems to be a fairly simple prescription for this: use the slider more, but also ease off the sinker. I know it's easier said than done; I noted this when I wrote about Matt Shoemaker that pitching is more nuanced than just replacing one pitch with another. Sequencing plays a huge role. But, for Keuchel, it's also an identity thing. Keuchel is the sinkerballer (or one of them, at least). He's the ground ball king. That's his pitch, man.

But hitters have just taken advantage of it. They haven't hit it especially hard, but the .379 BABIP allowed may be the function of more than just bad luck. And, while the pitch accounted for the fourth pitch of about 57% of his walks in 2015, that rate is up to 68% this year.

Or maybe it's the change-up that's more problematic. Right-handed hitters have absolutely teed off on his change-up, allowing fewer ground balls and almost twice as many home runs per non-ground ball. I gave the sinker a bad rap -- and, indeed, it hasn't been great, for being his bread-and-butter offering -- but has allowed a .283 ISO against this year. One hundred and sixty-four pitches still seems like a small sample, so maybe there's opportunity for regression to a happier mean.

Looking Forward

The increased slider usage from Keuchel is encouraging. He's using it a little more in all counts, not just when he's ahead. But the sinker is a moderate concern exacerbated into a severe one by sheer volume. And the change-up, which he throws almost exclusively to righties, is getting pummeled.

It may be too soon to say so, but Keuchel may need to entirely reinvent himself. It also may be too soon to say so but, if his last five starts are any indication, maybe he already is.

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