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Kevin Pillar's 2015 breakout, and some historical precedents

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Rick Osentoski-USA TODAY Sports

In the last month, it has been noted in various quarters that Kevin Pillar, in addition to stellar play in CF, has made some mechanical adjustments at the plate that might be bearing fruit. The result was that in the month of June, Pillar hit .365/.380/.531, good for a 153 wRC+ after having below average production in the first two months of 2015 and the prior years of his career.

In breaking down what drives a player's offensive production, I usually start with four stats: strikeout rate (K%), walk rate (BB%), isolated power (ISO), and BABIP. This covers basically all aspects of offensive production, while minimizing double counting and overlapping skills. As such, I was a little skeptical of Pillar's June representing a fundamental breakout considering the biggest difference was Pillar's .392 BABIP, which will not be sustained over time. He still wasn't walking, didn't hit for much power, and struck out at a similar rate to previous months.

What I didn't realize however, was the extent to which Pillar has cut his strikeout rate each month in 2015 compared to his stint in 2013-14. I've taken each of the four metrics referenced above, and charted Pillar's performance in both periods relative to the league average for position players:

pillar

Using adjusted metrics is easier for comparison, just like using ERA- rather than raw ERA. What's interesting is that 2015 is more status quo than not. Pillar's BABIP is slightly higher, but almost right bang on league average in both years. Likewise, his power is virtually unchanged, though below average. He's actually walking a little bit more, though still well below average.

But his strikeout rate is a different story: he's gone from significantly higher than league average in the mid-20% range to significantly better than average at 16%. This is the crux of his improved production, turning a weakness into a strength. It alone is worth about 2 runs per 100 plate appearances, or about 20 points of wRC+; a gamechanger if it can be sustained or mostly sustained into the future.

In general, there's good reason to be optimistic about that. Strikeouts tend to very strongly reflect player skills as opposed to external factors or luck, so even a half season sample of 355 PA is very meaningful for predicting the future. Accordingly, ZiPS and Steamer are forecasting a 16-17% rest-of-season K%, essentially going all-in on what he's done in 2015.

In spite of that, I'm naturally reticent to accept that such a huge change is likely to almost fully persist. While strikeout rates don't generally need much regressing, is it the same when there's such a huge change? Regressing to even league average (halfway in between) would be significant, about 0.75 WAR over a full season. So I thought it would be useful to look for some historical precedents - players with as similar a profile to Pillar as possible, who had a similar improvement in strikeout rate in the past, and whether they sustained it.

I filtered through the last 40 years, looking for players who debuted in the majors around age 23-25, accumulated a couple hundred plate appearances with a poor K%, and then subsequently significantly improved, ideally from worse than average to better than average. I was actually pleasantly surprised as it turns out there are some very good comparable players who were able to sustain a breakout. A handful of the best comparables are profiled below in more detail, a good number especially familiar.

After his age-24 season, Joe Crede had 279 PA in which he struck out 18% more than league average. The next year he was 19% less than league average, and he settled around 10-20% better for the rest of his career. While, an infielder, I think he's an interesting comp for Pillar as premium defender who was worth 13 WAR despite a career 90 wRC+. Pillar won't hit for the same power, but also won't be a popup machine that kills his BABIP.

Mark Grudzielanek broke in with the Expos in 1995 with a strikeout rate around league average. The next season and for the rest of his career, he was elite at avoiding strikeouts, a similar magnitude of improvement to Pillar. Again, an infielder, but whose value was primarily defensive, totally 23 WAR as a slap-hitting 90 wRC+ hitter who didn't walk much.

Mark Johnson struck out about 50% more than league average in 272 PA mostly at age 24. He got that down to league average and maintained that, though was not a valuable player since he could neither hit for power or average which doesn't work no matter how little one strikes out.

At age 24, Jeff Kent broke into MLB with 343 PA in which he struck out 50% more than average. The next season, he cut that back to 10% above average, maintained that for a while, and again improved it with age. Really not the best comp to Pillar, but obviously familiar to Jays fans.

Jed Lowrie had 383 PA through age-25, striking out 34% more than average. The next year, he knocked that down to 30% less than average, albeit in just under 200 PA. Not surprisingly, he hasn't matched quite that level since, but has settled in under league average while being a productive hitter. Pillar likely won't walk as much, but otherwise fits the offensive profile, and Lowrie has managed to total 12 WAR despite injuries and signed for 23-million this winter.

Pat Tabler struck out almost 80% more than average in 223 PA through his age 24 season before bringing his K% down just below league average, where it stayed for his prime years when he was a productive hitter. In his last couple years, he actually posted elite strikeout rates.

I could go on, but these are some of the best comparables for what Pillar has done. I've got a list of at least another 40 players who more or less did the same, but are less directly comparable. But I think this suffices to show the point that what Pillar has done is not unprecedented at all, and is not likely to turn into a pumpkin when midnight strikes. Or at least not because he goes back to striking out all over the place. And who knows, maybe he can further improve the walk rate.