FanPost

Hector Rondon: Mechanics Issue

Troy Taormina-USA TODAY Sports

In recent weeks, Hector Rondon’s performance as an Astro relief pitcher has been in decline. Since September 3rd his ERA has increased from 2.09 to 3.16 as of September 24th. More significantly, his WHIP has increased from 1.14 to 1.33 during this stretch. Both are huge jumps in such a short period of time and certainly indicates an underlying issue.

On Tuesday Rondon pitched a scoreless inning in the Astros game against the Blue Jays. Jake Kaplan mentioned in The Athletic that the Astros and Rondon had made changes before this game due to a detected "mechanical flaw in his delivery that wasn’t allowing him to get as much extension." [1]

Rondon’s improved results Tuesday are a step in the right direction and we will see if this trend holds over a larger sample size. In the meantime, let’s still take a deeper look and see if there are any indicators for a mechanic issue in his delivery. The three categories we will be looking at include Pitch Outcomes, Pitch Trajectory and Movement, and Pitch Location.

Pitch Outcomes

Let’s start by looking at pitch outcomes. For consistencies sake, I have broken up all following data into two categories: 3/29/18 to 9/3/18 and 9/4/18 to 9/24/18.

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Table Source: Brooksbaseball.net, Powered By Pitch Info

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Table Source: Brooksbaseball.net, Powered By Pitch Info

Below is a different look at the data in the form of percent change for both the fourseam fastball and slider, which are Rondon’s most used pitches.

y4mrj78dLR1nxyDCPr8y3LkR7pt7f0vBYXolp7AwNyDbocrWhwoK5A3A4Pff8bUigzrSG5ofUQlxGNrARstPdX-rL-ebbzcMX9Zmk4fbrMAnAH3gaBzEYzEaSN1XaBNHd6rBzA-cg96uQjaVZutYEYhf6kNUVhJ18vt7P1v_WPUxPNZhBVLjoPzrwVZz6wnpfLP2FAuQubU_hJIC-VdzzV8Tg.0.jpeg

There is a lot to unpack here, but I will focus on the trends that seem the most significant. Keep in mind that the sample sizes are much smaller during the month of September, so the data will be somewhat skewed.

For the fourseam fastball, the noticeable trends are as follows below.

- Groundball Percentage down 56%

- Line Drive Percentage up 87%

- Homerun Percentage up 581%

For the slider the noticeable trends are as follows below.

- Balls In Play Percentage up 66%

- Groundballs up 83%

- Line Drives up 330%

For the fourseam fastball, we see a smaller percentage of balls on the ground and a much larger percentage of balls hit hard (line drives and home runs). For the slider, we see a general increase in balls put in play and an increase in balls hit hard (line drives). Both are not good trends and add additional context to Rondon’s struggles during this time. However, they don’t conclusively point to a mechanic issue.

Pitch Trajectory and Movement

Now, let’s look at pitch trajectory and movement data.

y4moBBjvD4VQGu3n4EK44nhbCCYCRAuANETMPmJmk4aWbTz2S97CR-JHkigay5UCMJuSf_DHkpmW-S6PtQM7du0nNc3ODu95-Ef-fdkYo39RnDaooX0VhU3MEmrEKQ6c6L7IspoZu67EK2OEn19I0Uy7LXFh-ZoD_c6o1jCeUq6TRQCfye3tFe8dDjaHncudpQ8a7S5FFAILvb8vh0_V7RDxw.0.jpeg

Table Source: Brooksbaseball.net, Powered By Pitch Info

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Table Source: Brooksbaseball.net, Powered By Pitch Info

Here’s another look at percent changes for the Fourseam and Slider between these two time periods.

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Looking at the data from both an absolute and percent change point of view, we can see that there are a lot of categories that have mostly stayed the same, with a few categories showing noticeable changes.

The categories showing noticeable changes include pitch frequency and pitch movement, specifically horizontal movement with the fourseam fastball and vertical movement with the slider. Though these trends are there, and they certainly could be indicators of a mechanic issue, we can’t be sure if this is tied to his apparent mechanic issues or if these are just normal fluctuations over the course of a long season.

Something else of note is Rondon’s increased reliance on the fastball during this time period. Though this is interesting and worth keeping in mind, to me it doesn’t point directly to a mechanic issue.

Pitch Location

For our final set of data, let’s look at how Rondon’s pitch locating changed between each time period. The three categories we will look at our All Pitches, Fourseam, and Slider.

All Pitches

3/29/18 to 9/3/18

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Table Source: Brooksbaseball.net, Powered By Pitch Info

9/4/18 to 9/24/18

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Table Source: Brooksbaseball.net, Powered By Pitch Info

Again, we are dealing with smaller sample sizes in the second data set. However, I think there is enough to see significant changes in his ability to locate his pitches. During most of the season, Rondon was spotting his pitches low, away, and outside the strike zone and down, in, and within the strike zone. Over the month of September that trend appears to have broken down with less balls spotted low, away, and outside the strike zone and more balls spotted inside the strike zone.

Fourseam Fastball

3/29/18 to 9/3/18

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Table Source: Brooksbaseball.net, Powered By Pitch Info

9/4/18 to 9/24/18

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Table Source: Brooksbaseball.net, Powered By Pitch Info

For most of the season, his fastball location varied a bit, but was found primarily low/middle inside the strike zone and away and outside the strike zone. In the month of September, this trend also broke down. During this time more of the balls were found up in the zone, specifically on the corners.

Slider

Next let’s look at how the slider location has changed across this time period.

3/29/18 to 9/3/18

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Table Source: Brooksbaseball.net, Powered By Pitch Info

9/4/18 to 9/24/18

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Table Source: Brooksbaseball.net, Powered By Pitch Info

Again, his slider trends that held for most of the year broke down in September. For most of the year, his slider was primarily located low, away, and outside the strike zone. Over the course of September, you can see these balls not only drift low, away, and inside the strike zone, but also over the middle of the plate and even inside. Dangerous territory to be placing a slider.

Putting It All Together

In summary, I think the data is overwhelmingly pointing to a mechanic issue that developed in Rondon’s delivery after September 3rd. The pieces of data that support this conclusion to me include: large increases in balls hit hard (line drives and homeruns), subtle changes in horizontal and vertical movements of his pitches, and the loss of ability to locate his pitches consistently.

As previously mentioned the Astros and Rondon have apparently identified that there was a mechanic issue in his delivery. This could have led to his sudden improved pitching performance on Tuesday. However, repeated positive results will prove this case conclusively.

Sources:

[1] Kaplan, J. (2018, September 28). The six biggest questions facing the Astros before the ALDS. Retrieved September 24, 2018, from https://theathletic.com/553640/2018/09/28/the-six-biggest-questions-facing-the-astros-before-the-alds/

As Noted: All data and data tables sourced from Brooksbaseball.net