How Contact Ability Might Influence a Hitter’s Transition to the Majors

Back in February, there was some discussion about the transition from Triple-A to the majors, and whether that jump was getting any more difficult. It certainly seemed that way. Several highly-regarded minor leaguers completely flopped in their first tastes of big league action last year. Gregory Polanco, Jon Singleton, Xander Bogaerts, Jackie Bradley Jr. and the late Oscar Taveras all didn’t hit a lick after tearing it up in the minors. And perhaps worst of all, Javier Baez — a consensus top 10 prospect heading into the year — hit a putrid .169/.227/.324 with an unsightly 41% strikeout rate.

Jeff Sullivan and Ben Lindbergh both looked into the validity of this phenomenon, and wrote response articles more or less debunking it. Both concluded that the gap between Triple-A and the majors wasn’t growing after all, or at least not in any meaningful way. So much for that.

However, after thinking about it for a while, I started to wonder if there might be other ways to explain the initial failures of guys like Baez. Perhaps it might be more informative to look at these transitions from a different angle: Not across time, but across skill sets.

Baez’s flaws were easily identifiable. He struggled to make contact, and also showed a tendency to chase pitches out of the zone. But perhaps his rough transition wasn’t unique to him. Maybe his skill set — his poor plate discipline and/or poor bat-to-ball ability — just doesn’t play well against major league pitching. If that’s the case, it might help us be wary of the next Javier Baez.

KATOH — my prospect projection system — theoretically accounts for phenomenons like this to an extent. It uses individual statistics — most notably BB%, K%, ISO and BABIP — to forecast future performance, which allows for each of these metrics to be weighted individually. But a hitter’s statistics still only tell part of the story, as hitters can arrive their numbers through very different means.

As an example, Carlos Gomez and Austin Jackson are very different hitters. Gomez swings at practically everything, while Jackson is one of the more selective hitters in the game. Yet they both had strikeout rates of 22% and walk rates of 8% last year, respectively.

With this in mind, I thought I’d try to dig a little deeper. Using data from Minor League Central, which goes back to 2011, I played around with some plate discipline and contact metrics to see how they correlated with a hitter’s transition from Triple-A to the majors. I measured a hitter’s transition as his MLB wOBA subtracted from his Triple-A wOBA. My sample included all major league rookies over that span who also logged at least 200 Triple-A plate appearances in either their rookie year or the year before.

Most of the metrics showed little or no correlation. I couldn’t get anywhere with O-Swing%, Z-Swing%, O-Contact% or Zone%. But I did stumble upon one metric that seemed to have some value in predicting a hitter’s transition to the majors: Z-Contact% — a hitter’s contact rate on pitches inside of the strike zone.

The sample here isn’t huge, and the data don’t fit the trend line all that well, but the relationship is statistically significant for both wOBA and wRC+. The more contact a hitter makes on swings in the zone whilst in Triple-A, the more smoothly he transitions to the big leagues. Or at least that’s what it looks like. Check out these correlations.

I’m hesitant to say anything definitively, but it sure seems as though there’s something going on here. This isn’t merely an an instance of Z-Contact% acting as a proxy for a hitter’s strikeout rate, either. There’s almost no correlation between a hitter’s Triple-A strikeout rate and his wOBA differential.

Another interesting wrinkle is that Z-Contact% is better correlated with a hitter’s transition than plain old Contact%. My guess is that this is because Z-Contact% acts as a better proxy for a hitter’s bat-to-ball ability. Contact%, on the other hand, is influenced by a hitter’s plate discipline. Pitches outside of the strike zone are harder to hit, so players who swing at more of those pitches will have lower contact rates. Only looking at pitches in the zone does a better job of getting at a hitter’s actual contact skills.

The relationships are a little more clear when we zoom in on specific aspects of a player’s performance, like his strikeout rate.

Or isolated power.

Or BABIP.

It’s not immediately clear why high-contact hitters might have a relative advantage against higher-quality pitching. Maybe they have an easier time catching up with major league fastballs. Or perhaps their Triple-A performance was less reliant on their crushing meatballs thrown down the heart of the plate. Mistake pitches almost certainly come around less frequently in the major leagues.

It’s also possible that this might be more noise than signal. Any time you’re analyzing a group’s performance from one time period to another, you run the risk of encountering survivorship bias: The logical error of excluding players who didn’t show up in the second sample for one reason or another. It could simply be that high-contact hitters get shorter leashes, and are therefore less likely to get 200 big league plate appearances if they’re not hitting well.

In any event, let’s look at some current Triple-A players to see how all of this math might apply. Based on my findings, here are some prospects who spent significant time in Triple-A last season, and might be better big leaguers than you’d think based on their raw minor league performances.

Player	Age	Z-Contact%	Expected Change in wOBA due to Z-Contact%
Ronald Torreyes	22	94%	+.019
Jose Martinez	29	93%	+.016
Hernan Iribarren	31	93%	+.016
Rey Navarro	25	93%	+.016
Jose Pirela	25	92%	+.016
Eric Farris	29	92%	+.016
Corban Joseph	26	92%	+.016
Jermaine Curtis	27	92%	+.015
Tucker Barnhart	24	91%	+.014
Sean Kazmar	30	91%	+.013

And here are a few who might endure tough transitions.

Player	Age	AAA Z-Contact%	Expected Change in wOBA due to Z-Contact%
Jeremy Moore	28	67%	-.033
Matt Fields	29	68%	-.031
Kyle Skipworth	25	68%	-.031
Cody Decker	28	70%	-.027
Kevin Mattison	29	71%	-.025
Domingo Santana	22	71%	-.025
Vince Belnome	27	72%	-.024
Joc Pederson	23	72%	-.023
Jared Mitchell	26	72%	-.023
Max Stassi	24	72%	-.023

Several of these players aren’t really prospects. Although they haven’t crossed the 130 at bat threshold needed to forgo rookie eligibility, they’re unlikely to play any meaningful role in the big leagues. I’m sure you didn’t read this far to learn that Hernan Iribarren might be a slightly better hitter than you thought. So lets look at some of the baseball’s more relevant prospects. Here’s what these data tell us about the Triple-A hitters who ranked among Kiley McDaniel’s top 200 prospects this past winter. This only considers Triple-A stats, and includes prospects with at least 200 plate appearances in Triple-A in 2014.

Player	Age	AAA Z-Contact%	Expected Change in wOBA due to Z-Contact%
Stephen Piscotty	24	90%	+.011
Rob Refsnyder	24	87%	+.005
Steven Souza	26	86%	+.003
Deven Marrero	24	86%	+.003
Maikel Franco	22	82%	-.004
Randal Grichuk	23	81%	-.005
Christian Bethancourt	23	81%	-.006
Garin Cecchini	24	81%	-.007
Andrew Susac	25	80%	-.009
Kris Bryant	23	74%	-.020
Joc Pederson	23	72%	-.023
Domingo Santana	22	71%	-.025

And here it is in chart form.

All of this is interesting, but I’d recommend you take it with multiple grains of salt. Minor league zone and swing data can be a little shoddy, and analysis of shoddy data can lead to shoddy results. Additionally, as I alluded to earlier, there might be some selection bias at play among the group of hitters considered. And finally, both the number of observations (80) and the threshold for what goes into those observations (As few as 200 PAs) are smaller than we’d like them to be, making it difficult to do anything resembling a rigorous analysis. There may or may not be much to this, but at the very least, its something to think about for now.

Bat-to-ball ability is obviously a great tool for a hitter to have. We already knew that. But these data suggest that — for whatever reason — it might be even more important when facing major league pitching. If true, this could help explain the downfalls of recently highly-touted prospects like Mike Olt, Jon Singleton and Jackie Bradley Jr., who are already flirting with the “bust” label. It could also be the reason why contact machines like Brock Holt, Scooter Gennett and Jordy Mercer managed to sneak up on many of us.