Sabermetric Series, Part 3: Plate Discipline

Welcome to Part 3 of this Sabermetric Series. In previous installments, we discussed a batter’s quality of contact, batted ball distribution, familiarized ourselves with various metrics, and applied those things to player splits.

Previous Installments

Sabermetric Series, Part 1: Quality of Contact and Batted Balls

Sabermetric Series, Part 2: Applying Metrics to Splits

In this edition, we round out hitters by taking a look at their plate discipline. Plate discipline is important because it can help you discern whether or not a player’s surface stats are legitimate. For example, if a player is hitting .325 but has a 65% contact rate, 50% chase rate, and 15% swinging strike rate, you can tell pretty quickly that said player’s .325 average should be coming down in a big way. Here is a list of the plate discipline stats we’ll be looking at today:

• O-Swing% (percentage of the time a batter swings at pitches outside the strike zone; also referred to as “Chase Rate”)
• Z-Swing% (percentage of the time a batter swings at pitches inside the strike zone)
• Swing% (overall percentage of the time a batter swings, per pitch)
• O-Contact% (percentage of the time a batter makes contact on a pitch outside the strike zone)
• Z-Contact% (percentage of the time a batter makes contact on a pitch inside the strike zone)
• Contact% (overall percentage of the time a batter makes contact, per swing)
• Zone% (percentage of pitches the batter gets inside the strike zone)
• F-Strike% (aka First-Pitch Strike Rate; percentage of strikes a batter gets on his first pitch, per plate appearance)
• SwStr% (aka Swinging Strike Rate; percentage of swings that do not result in contact)

Go ahead and pull up any player page on Fangraphs and follow along with this, if you wish. These stats are way down on the player page, but they are very important if you want to get a true sense of a player’s skill set and approach. We’ll start with O-Swing%, or Chase Rate, as I like to call it. It refers to pitches outside the zone that a batter swings at, commonly known as “chasing” what is often times a bad pitch. This tells you how good a hitter is at laying off of bad pitches, a key to good discipline. The league-average O-Swing% is about 30%; the player with the lowest O-Swing% in 2017 was (no surprise at all) walk machine Joey Votto, at 15.8%. Votto is probably the most disciplined hitter in baseball, and one look at his absurd 19% walk rate tells us immediately how beneficial it can be to lay off pitches outside the zone. This number can feed into your walk rate quite a bit. On the other hand, the league leader in O-Swing% was Corey Dickerson at 45.6%. More aggressive hitters will expand the zone and have a higher O-Swing%, also resulting in fewer walks. It’s no surprise that Dickerson also walked at a well below average rate of 5.6%.

Z-Swing%, or the rate of swings per pitch in the strike zone, is a number you want to be high. Unlike pitches outside the zone that typically result in weak contact, swinging at pitches inside the zone leads to better contact. If you’re letting pitches in the strike zone sail right by for called strikes, you’re being too passive at the plate. That is a lesser-known potential detriment with batters. The league average Z-Swing% is around 65%; the leader in 2017 was Freddie Freeman, who had an 84.2% rate. He wound up with an elite .407 wOBA. Conversely, the league laggard, if you will, was Xander Bogaerts with just a 53% Z-Swing%. He refused to swing at hittable pitches, leading him to a very disappointing season and a wOBA that wound up at a league-average .321.

Swing% is simply the rate of swings per pitch. This number tells you a lot about whether a batter has an aggressive approach at the plate, or whether he is more patient and sees a lot of pitches. The average major leaguer swings at around 45% of pitches; in 2017 it was Avisail Garcia, who led the league with a 59% Swing%. You will also see that this number often coincides with the players who reach the most out of the zone, which makes sense — more swings, more reaches. However, not all of those pitches are good ones to hit. Matt Carpenter, who also had one of the lowest chase rates in baseball, had the lowest Swing% at 34.1%. Understanding this now, it makes sense that Carpenter was fourth in MLB in BB% at 17.5%, and Avisail Garcia was 24th worst in BB% at 5.9%.

Now we move on to the contact metrics. O-Contact% is the amount of contact a batter makes on pitches outside of the zone, which is generally a bad thing unless your name is Corey Dickerson. Connecting on pitches outside the zone more commonly leads to weak contact such as softly hit fly balls and grounders, which, as we established in Part 1 of this series, is the opposite of good. The league average O-Contact% is around 65%, with the league leader being Andrelton Simmons at 79.9%. The contact-adverse Joey Gallo brings up the rear at 42.6%. There are plenty of good players that can make a high O-Contact% work, but, generally speaking, those players are contact-oriented and don’t get a lot of power from that approach.

Z-Contact% is the amount of contact on pitches in the strike zone, which is a very good thing. These are the pitches you can drive, and if you’re missing on a lot of pitches in the zone (which should be the easiest pitches to hit), you’re going to struggle to hit for average. The average Z-Contact% is around 87%. Melky Cabrera led MLB in 2017 with a 95.1% mark, while Joey Gallo again finished in dead last by a mile at just 71.6%. This was one way I was able to identify Jose Bautista’s 2017 decline being legitimate early on; his Z-Contact% dropped a whopping 4.4% from 2016. That’s a terrifying decline.

Contact% is, as it sounds, the overall percentage of contact you’re making per swing. MLB average is around 80%, with Joe Panik leading the league at 89.9% and (you guessed it) Joey Gallo posting the worst mark at a horrifying 59.1%. Different approaches lead to much different contact rates, so you can’t just say that more or less contact is necessarily better. Gallo doesn’t care about average; he just wants to hit dingers. So, he swings out of his shoes all the time and throws any semblance of a two-strike approach to the wind. I use the 70% threshold as the mark where I start to worry about a player making too little contact. If you’re making less than 70% contact, you’re really going to struggle to hit for average. There are plenty of power hitters that make a 70% contact rate work, but they make up for it by hitting the ball really hard to inflate their BABIPs.

Zone% tells us how many of a hitter’s pitches are in the strike zone. The higher the number, that generally means that pitchers aren’t scared of the batter and challenge them a lot by pounding the zone. The lower the number, that generally means that the pitcher either knows the batter will chase out of the zone, or that he’s afraid to throw the batter strikes. MLB average is around 44%, with Dee Gordon leading the league at 50% and (yes, again) Joey Gallo in last at 36.1%. Given the numbers we’ve seen from him so far, why would you ever throw him a strike?

First Pitch Strike Rate (F-Strike%) doesn’t tell us a lot about hitters. That’s more beneficial when evaluating pitching, so we’ll discuss that then. Instead, we’ll finish this off with SwStr%, or Swinging Strike Rate. This is the percentage a batter swings and misses per pitch. League average is around 9.5% … and I’ll give you one guess who had the highest mark in 2017. Oh look, it’s Joey Gallo at 19.3%. The lowest rate went to Joe Mauer at just 4.1%. Swinging Strike Rate coincides heavily with Contact%, so when you see a high Swinging Strike rate, you can generally expect a low Contact% and therefore a lower batting average.

An interesting player to finish this off with is the aforementioned Avisail Garcia. In 2017, he had a 72.4% Contact%, 16.2% SwStr%, and 39.8% O-Swing% that are all similar to his career rates. None of those numbers is good. Yet somehow he hit .330 as opposed to his career average of .277. He managed a .392 BABIP, which is absurd even given his 35.3% Hard%. It sounds extreme to project anyone to have a 50 point regression in batting average, but that’s exactly what I expect to happen with Garcia in 2018 after looking into his plate discipline.

Next time, we move on to pitchers and dive into ERA estimators such as FIP and SIERA. Until then, stay disciplined!