May 6, 2016

Nick Mariano continues his fantasy baseball strategy series with a look at plate discipline metrics, and how to use them to win your league.

Welcome back to the fantasy baseball classroom where we’re learning about advanced statistics that give us a leg up on the competition, and help us win our fantasy baseball leagues.

Our first articles were about a hitter’s BABIP as well as hard-hit rates. We then looked at pitchers and their SIERAs. If you didn't get a chance to read those yet, well, you should.

Now we turn back to hitters, and we’ll be checking in on some plate discipline metrics that go well beyond walks and strikeouts. Let's get to it.

The Importance of Looking Beyond Strikeouts and Walks

It used to be perfectly acceptable to say that Player X strikes out or walks “a lot” in conversation, but we can do better than that. Let’s look at a big power bat from last season, Nolan Arenado, to illustrate our points. Last season Arenado had a 16.5 percent strikeout rate with a 5.1 percent walk rate.

Arenado is currently mashing, but those stats overshadow what looks to be insane growth at the plate. As of this writing on May 4, Arenado is both walking and striking out 9.7 percent of the time. Now for the million dollar question, is this growth sustainable or just noise?

Here is where the fun can really begin. Instead of just looking at how often a player’s at-bat ends in a strikeout or walk, we can see how frequently they swing and miss, as well as how often they swing at pitches thrown outside of the zone. Why limit ourselves to evaluating the player solely by the end result when there are many data points from within the at-bats?

Advanced Plate Discipline Metrics

There are seven items on the agenda. That may sound overwhelming, but I promise that it all comes together neatly. Statistics such as these can speak to two things: how the batter is performing and how pitchers are attacking them. We’re focusing on the hitter here, pitchers come next. You can find Arenado’s dashboard for these stats here (and do the same for each respective player on Fangraphs).

 
Swinging Strike Rate
It’s what it sounds like, how often a player swings at a pitch and misses. Let’s stick with Nolan Arenado as his 2016 has shown growth. We covered how in 2015 he struck out 16.5 percent of the time, and this came with a 10.5 percent swinging strike rate. So far in 2016, Arenado has cut down his strikeout rate to 9.7 percent! How much should we believe? Well for starters, his swinging strike rate has dropped to 6.8 percent thus far. Very interesting, and that certainly leads one to believe there might truly be something here.

 
Swing, O-Swing and Z-Swing Rates
Apologies for throwing three things at you at once, but this works well if you can picture the batter and pitcher locked into battle. These rates for looking at how often a player swings at pitches, both outside and inside the zone.

Let’s go one-by-one here:

Swing rate is simply the number of swings divided by the number of pitches seen. This can speak to overall patience.

O-Swing rate is the number of swings at pitches out of the zone over total pitches out of the zone. Colloquially this can be referred to as “chase rate”, or how often a batter “chases” a pitch outside of the zone.

Z-Swing rate is how often a player makes contact with pitches in the zone over total pitches in the zone. This can shine light on how selective a batter is.

On their own, these stats can’t really provide too much insight. Once a player has a baseline though, then you can really identify changes – for better or worse.

Here are Arenado’s respective Swing rate, O-Swing rate, and Z-Swing rate from 2015 and this season:

So what those numbers say is that Arenado is:

1. Swinging less in general.
2. Chasing less pitches out of the zone.
3. Swinging at less pitches in the zone.

 
Still with me? Good, because it looks like we’re really onto something here. Arenado appears to have unleashed a new approach in the early going, but just because he is laying off more pitches doesn’t mean he is more successful when he swings. These next stats can help fill that gap.

 
Contact, O-Contact, and Z-Contact
These rates speak to how often hitters make contact with said pitches. You’ll see the same trend from the first set apply here:

Contact rate is the number of times contact was made with a pitch over total number of swings. Making contact is important.

O-Contact rate is how often contact was made on pitches out of the zone over total swings out of zone. There are several hitters who are notorious for still succeeding even on pitches thrown out of the zone. Vladimir Guerrero comes to mind.

Z-Contact rate is how often contact was made on pitches in the zone over total swings in the zone. Those pitches in the strike zone are ideally more hittable.

Here we go again with Mr. Arenado:

 
Hey now, positive indicators in every single category. He really does seem to be growing in his fourth big league season.

The Big Picture

Now instead of simply looking at whether a guy has struck out or walked, you now have context to analyze how valid the results are to the batter’s process.

It is also imperative that you pay close attention to each respective player’s traits. Do not compare a speedy contact hitter to a big power bat. Comparing a player’s career rates to his current season can be useful, but the most ideal comparison is usually going to be their most recent season.

Sometimes the numbers are not so clean-cut. How about a player whose strikeout rate has gone from 21.2 percent to 21 percent despite big changes in swinging strike rate (13.9 to 17.2 percent) and O-Swing rate (33.7 to 41.4 percent). This player’s plate discipline points to more strikeouts, not less. It’s Yasiel Puig, by the way.

As with every other statistic, no one number or set can tell the whole story. Perhaps a batter is being attacked with more off-speed or breaking pitches. Seeing more inside pitches rather than outside, high versus low, etc. Maybe they’re seeing the same pitches, but struggling with sliders this season. We’re here to examine the bigger picture.

Now you have a much better idea of how well a hitter is swinging the bat. These are more tools with which you can inspect a hot or cold start, identify over and under-performances, and most importantly, further understand the beautiful game of baseball. Did I say that? I meant to crush your competition with, obviously.

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