The 2016 Starting Pitcher Strikeout Rate Downsiders

Two years ago, I shared with you an updated version of my xK% equation. The formula uses a trio of strike type rates found at Baseball-Reference.com, including a pitcher’s looking, swinging, and foul strike percentages, along with his overall rate of strikes thrown. With an adjusted R-squared of 0.913, it explains a very higher percentage of a pitcher’s strikeout rate. Its best use is early in the season when the plate appearance (the K% denominator) sample size is still small, as xK% uses total pitches as the denominator, so we can reach a reasonable sample size to analyze much more quickly.

Yesterday, I shared the list of pitchers with strikeout rate upside, according to the xK% metric. It was a rather boring group of names, but did result in two recommendations. Today, I’ll take a look at the pitchers with apparent strikeout rate downside. These pitchers all posted strikeout rate marks well above their xK% marks. Like I did yesterday, I included all pitchers that posted a K% at least 2% higher than his xK%.

Well hmmm, this is quite a different group of names than yesterday! But of course, this makes perfect sense. In general, the low guys on the totem pole have likely bottomed out and have nowhere to go but up, while the top strikeout artists have probably maxed out and risk regressing.

We find a familiar name on top, the best pitcher in the world, Clayton Kershaw. This is a perfect opportunity to remind you of the following — the xK% equation is like every other formula ever developed in that it will project a narrower gap between the top end and bottom end than what actually occurs. It’s the nature of formulas. They miss the outliers, and that’s typically a good thing. If you’re curious, xK% actually didn’t think Kershaw deserved baseball’s highest strikeout rate. It thought Chris Sale did.

That’s certainly bad news for the Angels and Matt Shoemaker fans (do they still exist?). His strikeout rate declined marginally last year after a surprise 2014 rookie campaign, but xK% thought it should have slid even further. He was below average in every component of the xK% equation, as his slider, two-seamer, and curve all lost some of their whiffiness (I now declare that a word).

I was impressed with how quickly Patrick Corbin regained his pre-TJ surgery skills, but xK% thinks that maybe he wasn’t as good as we thought. Still, his velocity is up, he’s getting swings and misses, and he throws a ton of strikes. I still like him.

Perhaps on a full season basis, Stephen Strasburg lucked into a nearly 30% strikeout rate. But, we all know he was hurt early in the season which no doubt affected his performance, and we all know the dominant stretch he enjoyed to finish the season. He has a better chance of capturing a Cy Young award than most assume.

Since 2008, Jon Lester has outperformed his xK% in six of eight seasons. Clearly, he’s doing something not being accounted for. What that is, I have no idea. While that means that he shouldn’t be expected to regress to his xK%, the gap between the two was still his highest, meaning there should be some decline assumed.

Jerad Eickhoff has become a popular sleeper, though I wonder if he would be receiving the same love if his ERA was closer to 4.00, rather than the shiny 2.65 mark he posted. His slider was sensational over the relatively small sample, while his curve ball was also excellent. With a scouting grade of just 40/45+ on that slider, clearly the effectiveness of the pitch was quite the surprise. Was it a small sample fluke or somewhat sustainable? His appearance on the list is already the first red flag.

Yeesh, Trevor Bauer is nothing without a strong strikeout rate. What’s fun about Bauer is that he comes at hitters with the kitchen sink. What’s not fun is that not all of his pitches are actually good. Why he continues to throw his least effective pitches, rather than consolidating, really baffles me. I think he has the stuff that makes him capable of a strikeout rate surge, but he needs to change his pitch mix.

It was a dream season for Jake Arrieta last year and it has really been incredible to see his transformation from prospect bust to one of the best pitchers in baseball. Clearly fantasy owners are confident in a strong follow up as he’s going third among starters in NFBC and 20th overall. However, of all the top tier pitchers this season, he scares me the most (I still had him ranked sixth among starters in LABR). He doesn’t throw any elite pitches, just a collection of very good ones, I’m not sure that ground ball rate is sustainable, and he doesn’t throw enough strikes to post a walk rate that low. I won’t be owning any shares of his this year for sure at his going rate.

Man, for a southpaw who averages in the mid-90s with his fastball and throws two pitches with mid-teen SwStk% marks, you wonder how James Paxton doesn’t strike out more hitters. I still love the overall skill set and the seeds are definitely here for a major breakout. Obviously, health is the big question mark. Also, where does he even fit in the rotation with Nate Karns now aboard?

Aaron Nola turned excellent control and a fantastic curveball into a respectable rookie debut. His fastball, though, was rather putrid at generating swings and misses and overall, he induced whiffs at a well below average clip. It’s unlikely he sustains such a high rate of called strikes, so he’ll probably need to raise his rate of swinging strikes to ensure his strikeout rate doesn’t fall.

Dallas Keuchel has ridden a wonderful slider/changeup combination to new heights, while also doing major harm to the worms of America. His xK% suggests skepticism about this newfound strikeout ability, and anytime a pitcher suddenly enjoys a strikeout rate spike, you have to look at it with a questioning eye. But even if that rate does decline, his ground ball rate gives him so much margin for error.

I’m both elated and saddened that everyone is now on the Carlos Carrasco hype train. I still maintain that I discovered him first, despite this fun back and forth…

@BaseballATeam @enosarris race to see who wrote the first article about him?

— Mike Podhorzer (@MikePodhorzer) December 17, 2015

Now with everyone loving him, his price has skyrocketed and isn’t matching his 2015 ERA, which means I can’t buy him at a discount, which makes me sad 🙁 So for anyone in any of my leagues reading this, LOOK AT THIS POTENTIAL STRIKEOUT RATE DOWNSIDE! STAY AWAY!