Pitch f/x and Tanner Houck’s Breakout Season

Tanner Houck

A change in pitch usage can be the catalyst for a pitcher breaking out. In this article, we will go through the process of using Pitch f/x data via Fangraphs to identify how the Boston Red Sox’s young hurler Tanner Houck changed his pitch mix by changing his usage rates of existing pitches. With data from Fangraphs, we will use Excel to examine Houck’s potential for a breakout season closely.

What is Pitch f/x?

Pitch f/x is a system maintained by Sportvision that uses three permanently mounted cameras to track the speed and location of a pitched baseball from the pitcher’s mound to home plate. Pitch f/x debuted in MLB during the 2006 playoffs. The system is in every ballpark as it has been at the forefront of the analytics movement prevalent in today’s game.

Our Process of the Data

Our method starts by visiting Fangraphs to collect the data we need. From the 2021 pitching leaders page, we will generate a list of all MLB pitchers who threw at least 40 innings; this allows us to include starters who may have started pitching towards the end of the year have been shut down early due to injuries.

Next, we’ll select the pitch type tab where the pitch f/x data is. You’ll see a complete list of pitchers, with the percentage breakdown of pitches they’ve thrown. After that export, convert it into a CSV file viewed via Excel. We’ll repeat this process for Houck’s first season of 2020 as well.

Why FB %?

We take the difference in fastball percentage because that can indicate that a pitcher has added more to their arsenal and relied less on the fastball to get by. With the right mix of pitches, a pitcher can drastically change their fortunes. Before we dive into examples, it should be noted that we are going to be referring to the Fangraphs definition of fastballs which excludes cutters and splitters. So two-seamers, four-seamers, and sinkers constitute FB%.

For example, let’s quickly examine 2021 NL Cy Young winner Corbin Burnes. Before 2021 Burnes was not the superstar we think of him as today (2.2 fWAR in prior three seasons combined). He relied heavily on a fastball (36.5.% of the time). Last season he sliced that percentage down to just 10.8%. Replacing those sinkers and four-seamers was an increase in cutters and curveballs. That formula equals a dominant season and the birth of a star (1.63 FIP in 2021). He increased his innings pitched per start, decreased his walks per nine innings, and posted career bests xERA and WHIP.

Another example is Miami Marlins young ace Sandy Alcantara. Alcantara’s fastball percentage decreased 9.8% from 2020 to 2021. What was the result? He established himself as the organization’s cornerstone and produced a career-best 4.2 fWAR. Replacing those fastballs with more changeups and sliders proved a great decision. He increased his innings pitched per start and posted career lows in WHIP, FIP, and xERA.

Tanner Houck

Enough of burying the lead, it’s time to discuss the possible emergence of Tanner Houck. 2021 was encouraging, especially after finishing the season with a good stretch. Houck pitched 24.1 innings in September and October with a 2.31 FIP and a 0.99 WHIP.

This offseason, there is still debate over whether he’ll be used as a starter or reliever for 2022, but his adjustment in pitch repertoire could be the key to him breaking out this upcoming season. Like the aforementioned Burnes and Alcantara, Houck decreased the number of fastballs from his debut campaign in 2020.

Using Pitchf/x data Houck decreased his fastball usage by 5.4% from 2020 to 2021. This decrease was the largest among current Red Sox pitchers from 2020 to 2021(see the spreadsheet). Yes, his 2020 sample size was a minuscule three starts ( 17 innings). When you look at rate stats such as FIP, walks per nine innings, and strikeouts per nine, Houck made improvements in 2021. With the dip in fastballs came a more versatile pitch mix. His slider usage increased 1.6% in 2021, and his splitter increased by 5.1%.

Houck found success whenever his slider became his primary pitch, especially as he went through the batting order for the third time. In months when his slider was his number one pitch, his FIP was 2.17 instead of a whopping 22.97 when his fastball was primary. If he continues to feature his slider and work his other pitches off of that, he could make a strong case as a starting rotation member.

Fantasy Bonus

For those who partake in fantasy baseball, monitoring those who decrease their FB% may be a helpful tool. Young guns like Alcantara,

Julio Urías and Pablo López became fantasy studs in 2021, and all three decreased their FB% and diversified their arsenal. All three of these names are in the top 35 fantasy pitchers, according to fantraxhq.com. Maybe Houck can be that under-the-radar gem. With his expanded repertoire, he’s following the mold that could put him in the ranks among the MLB’s best in fantasy and real life.

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Players Mentioned 

Tanner Houck, Corbin Burnes, Sandy Alcantara, Julio Urías, Pablo López