Pirates Hitters With Two Strikes: Part I

With the recent articles about Bryce Harper's new two-strike approach this year, I wanted to investigate how the Pirates hitters have fared this year with two strikes. I decided to compare the Pirates with the rest of MLB to see if any Pirates hitters stand out in their two-strike performance, and used this data to investigate certain players in more detail. All statistics in this article are current up to August 5, 2017, and include only those players with at least 30 at-bats that went to a two-strike count and 30 at-bats that ended with less than two strikes. In the first part of this two-part series on how Pirates hitters perform with two strikes, I focus primarily on launch speed (sometimes referred to as exit velocity). Three main factors contribute to launch speed: bat speed, quality of contact, and pitch speed.

This chart, which plots each hitter’s average launch speed with two strikes against his average launch speed without two strikes shows that hitters have slightly lower average launch speeds with two strikes. We will dive into individual players shortly, but this shows that the Pirates hitters’ launch speeds are fairly normal when compared to the rest of MLB.

Data from Baseball Savant

With that in mind, here are the Pirates hitters’ launch speeds with and without two strikes:

Across MLB, the average launch speed differential with and without two strikes is +0.79 mph, and the standard deviation is 2.26 mph. So, anywhere from a decrease of 1.47 mph to an increase of 3.05 mph with two strikes could be considered normal as that range encompasses one standard deviation from the mean. As shown above, more than half of the Pirates hitters fall outside that range.

Elias Diaz has such a small sample size, that his +3.6 mph launch speed with two strikes will probably correct itself over time. It's certainly something to keep an eye on when he gets called back up, but there isn't enough data today to make anything of it. Chris Stewart’s 1.5 differential is only 0.03 away from our normal range, and his career numbers are even more normal, so there is hardly anything interesting there. So, let's take a look at the names at the top of this chart — those hitters who have significantly lower launch speeds with two strikes. Josh Bell, Starling Marte, Jordy Mercer, Gregory Polanco, Josh Harrison and Andrew McCutchen all have launch speed differentials larger than Bryce Harper’s -1.5 mph and outside the normal range for MLB.

Marte appears to have the same swing with and without two strikes. His sample size this year is very small due to his suspension, and his career average launch speed is 85.8 mph (5.3 mph higher than his average of 80.5 mph this year), so we will look for it to get back to that career mark and see how his two-strike numbers change with that. If his launch speed does not make a comeback, he may not either.

Mercer does take a different approach with two strikes. He chokes up on the bat as many hitters do, perhaps most notably Joey Votto (who has also started choking up earlier in the count). With essentially a shorter bat because of this, Mercer’s otherwise unchanged swing will still result in slower launch speeds because the average speed of his bat will decrease. With two strikes, his estimated bat speed decreases by 3.7 mph according to Statcast. On its own, each mph of bat speed contributes 1.2 mph of launch speed (each mph of pitch speed only contributes 0.2 mph). This 3.7 mph decrease in Mercer's bat speed is more than enough to account for his 2.4 mph decrease in launch speed with two strikes.

McCutchen, Harrison, Bell and Polanco don't appear to make any changes to their batting stance, swing or grip with two strikes. However, the reasons for their slower launch speeds appear to be different. McCutchen's and Harrison's decreased bat speed is the likely culprit for their slower launch speeds with two strikes, despite their swings appearing the same regardless of the count. McCutchen's bat speed decreases by 1.8 mph with two strikes, and Harrison's decreases by 2.5 mph. These decreases are enough to account for their decreases in launch speed, so the open question for McCutchen and Harrison would be why their bat speed decreases with two strikes. It’s possible that, through trying to defend the zone and keep their bat in the zone longer with two strikes, both players slow their bats slightly to maximize chance of contact, but it’s difficult to see what changes in their swing to accomplish this slow-down.

Bell's launch speed differential is interesting not only because his swing appears consistent throughout the count from both sides of the plate, but because his decrease in estimated bat speed barely accounts for his decreased launch speed. With two strikes, his bat speed decreases 2.8 mph, accounting for 3.36 mph of launch speed. Perhaps he makes the same quality of contact no matter the count and bat speed is the sole factor affecting his launch speed, but we also have to take into account him being a switch-hitter. A greater percentage of his right-handed at-bats go to two strikes than his left-handed at-bats, and he is a weaker hitter from the right side of the plate (no matter the count), so his right-handed at bats with two strikes are bringing down that two-strike launch speed disproportionately.

Polanco's bat speed is practically the same with two strikes, only decreasing 0.1 mph. So, why does Polanco's launch speed decrease 1.9 mph when his bat speed only accounts for a 0.12 mph decrease? Statcast separates hits into six categories based on quality of contact:

1. Barrels
2. Solid
3. Flare/burner
4. Poorly under
5. Poorly topped
6. Poorly weak

Here are Polanco's splits with and without two strikes by quality of contact:

Polanco has not been making good contact with a ton of pitches, regardless of the count, as Jason Rollison noted in his piece over at Pirates Breakdown two months ago. While Polanco is barreling up a slightly lower percentage of balls with two strikes, the number that sticks out here is the number of pitches he's topping, meaning he is swinging above the ball and likely hitting it on the ground. This makes sense if we look at the heat maps of pitches he sees with and without two strikes.

Fangraphs

Every hitter's pitches-received heat map will change with two strikes as pitchers try to get a batter to chase outside the zone. In Polanco's case in particular pitchers are targeting the bottom part of the zone, throwing 29% of pitches down and out of the zone, vs only 16.7% without two strikes. Combining this statistic with Rollison's conjecture that Polanco doesn't see sliders very well, we can see how Polanco is topping balls down in the zone, he's getting targeted there with two strikes, and his two-strike launch speed is therefore suffering.

Launch speed is only one aspect of evaluating a hitter. As a raw metric, it is good at showing how well a hitter is seeing and connecting with the ball, but it hardly shows the full picture of a hitter’s performance. In the second part of this look at the Pirates hitters’ two-strike performance, I will be looking at more traditional hitting statistics, comparing the Pirates to the rest of Major League Baseball.