The Key to Success: Analyzing MLB Pitcher Performance from the 2020–2021 Season Title
By: Taylor Kim (Project Lead), Shiyu Murashima, Wolfe Pickett, Andrew Schweitzer
Summary: Pitcher performance is essential to having a successful season in MLB, but how do these pitchers perform under specific circumstances? What type of pitch does a pitcher throw to get a strikeout, do lefty-righty matchups matter, and do pitchers perform worse when they’re away? Find out more in our article!
Introduction:
If you’re a baseball fan or have played baseball, you probably understand how important of a role the starting and bullpen pitchers play in every game. Especially during the postseason and win-or-go-home games, the pitching can make or break your team. Our team was curious to see how these star pitchers perform under certain circumstances. What does the pitcher throw to get a strikeout, and how effectively do lefty-righty matchups work, and do pitchers do worse when they’re away? These are just some of the questions we sought to have answered by utilizing and cleaning the data from the 2021–2022 MLB season.
What was the go-to pitch for strikeouts last season?
We were curious to see what pitch type was most commonly used to record a strikeout. Of the 709,851 total pitches thrown by all pitchers throughout the entire season, our dataset recorded 41,973 strikeout pitches. After filtering out our data to only look at strikeout pitches thrown, we then sorted those pitches by pitch type. Using those proportions, we created a pie chart to display the variation.
Taking a look at our results, we can see the pitch types that pitchers used most to least often. This is important information, especially for the batter’s knowledge, because they might be able to predict what pitch is coming at an 0–2 or 3–2 count. The four-seam fastball was expectedly the most common strikeout pitch last season. This is expected because this is the most common pitch thrown by pitchers in general. Additionally, we discovered that more than half (58%) of the recorded pitches resulting in strikeouts were either four-seam fastballs or sliders. Changeups, sinkers, and curveballs fall next in line for most common pitch-types. We have strong evidence to believe that four-seam fastballs and sliders were the most successful pitch types in recording a strikeout during the 2020–2021 season.
Kershaw vs Ohtani
Now that we have a general understanding of the most common “strikeout” pitches, we were also curious to see how two superstar pitchers performed against these results. Shohei Ohtani won MVP for the American League in 2021 and was the first ever two-way player in the 2021 All-Star game. Clayton Kershaw has made 8 All-Star Appearances, won 3 Cy-Young Awards, and is a future Hall-Of-Famer. These incredible starting pitchers are well-known and loved by millions of fans in LA and across the world. But what makes these two pitchers so special? Do they follow the general trend when it comes to throwing a strikeout?
Using our data, we found that Shohei threw 2,027 pitches and Kershaw threw a total of 1,806 pitches in this season. We then filtered out those pitches to only observe their strikeouts. Shohei recorded 156 strikeouts and Kershaw recorded 144. Sorting these pitches by pitch type and displaying them on a graph, we were able to create a cohesive picture of Kershaw and Ohtani’s pitch types when striking out their batter.
KEY: CU (curveball), FC (cutter), FF (fastball), FS (splitter), SL (slider)
To no surprise, we found that Kershaw’s most successful “strikeout pitch” is his slider. This makes sense because the slider is his go-to pitch. We were surprised, however, by Ohtani’s results. His splitter, which he only throws 18% of the time, is his most effective pitch to get a strikeout. His fastball, which he throws 44% of the time, is actually his third most effective pitch, which makes up 22% of his total strikeouts. This is remarkable because one would usually expect that a pitcher’s most common pitch would get him the most strikeouts. But Ohtani’s versatility is what makes him such an effective and unpredictable pitcher.
Another reason that this graph is so fascinating is the fact that Kershaw and Ohtani’s individual pitch types do not reflect those of the whole. As seen in the pie chart that accounts for all pitchers in the league, the slider is thrown 26% percent of the time and the splitter is only seen 3% of the time. These are not common pitch types. But we see that Kershaw and Ohtani are remarkable in that they most commonly throw pitches that the majority of pitchers may not. And this is just one of many reasons that make these two pitchers so impressive.
Which Pitch Should I Avoid Throwing with Runners in Scoring Position?
Being a pitcher comes with a lot of pressure, especially during moments when you are at risk of giving up runs. So what should a pitcher do when they have runners in scoring position? As the pitcher, you want to record an out as soon as possible and make sure that no one scores. But pitchers can’t always be successful, and the batter might be able to outperform them and score some runs for their team.
So as a pitcher, what pitch should you throw in these high-stress moments? We took a deeper look into our data and focused only on the pitches when there is someone on 2nd or 3rd base. This left us with a total of 8,350 observations. We sorted these pitches even more and only looked at undesired outcomes, such as a double, single, triple, or home run; anything that the pitcher doesn’t want to happen. We then displayed these observations on a chart, where every pitch type is sorted by the frequency of those unwanted events. Here is what our results showed.
KEY: CH (changeup), CU (curveball), FC (cutter), FF (fastball), FS (splitter/split-finger fastball), KC (knuckle-curve), SI (sinker), SL (slider)
By sheer volume, the fastball (FF) is expectedly the most commonly thrown pitch, but that doesn’t necessarily make it the best option. As you can see it has a high percentage of walks as well as singles and sac flies. Based on the graph, it looks like the curveball (CU) would be a good option since there’s a large percentage of strikeouts and a relatively low percentage of walks and hits. The splitter and knuckle-curves might also be good alternatives since they aren’t as common and it may throw off your batter. However, these are difficult to throw during a high-pressure situation, and you take a larger risk of throwing a ball.
Do lefty pitchers have an advantage against lefty hitters?
A well-known fact in the baseball world is the idea of platoon splits — the difference between a batter’s performance against opposite and same-handed pitching? In essence, righty hitters do better against lefty pitchers, and lefty hitters do better against righty pitchers. Conversely, the same logic applies from the pitcher’s perspective. Psychologically, this statement makes complete sense. Seeing the ball coming from a pitcher of the opposite hand is much easier to perceive and hit, especially breaking pitches (e.g., sliders and curveballs). To prove this well-known fact, we analyzed MLB data from 2015 to 2019 to get some deeper insights.
To no surprise, same-handed matchups are preferable for pitchers. The graph above plots the proportion of common pitcher-hitter situations, such as a pop fly, fly out, strike out, or other, that results in an out. For same-handed matchups, left and right-handed pitchers have a 2.33 and 0.38 percent advantage, respectively, over their switch-handed matchup counterparts. This two percent plus difference makes left-handed handed pitchers a valuable commodity. Focusing on just strikeouts, the most common way to get out in baseball, our argument still stands. Same-handed matchups fare better than switch-handed matchups. Again, left-handed pitchers perform better on average compared to right-handed pitchers. When you factor in the scarcity of left-handed pitchers, their value and stock go even up. This hidden advantage, not explicitly supported by data, is attributed to the hitters’ lack of familiarity with pitches coming from the left side. From Madison Bumgarner, and Chris Sales, to Clayton Kershaw, left-handed pitchers have been a dominant force in recent MLB history.
Platoon splits don’t just apply to pitchers. Hitters have a significant advantage in switch-handed matchups. From looking at the graph that plots the proportion of at-bat situations that result in either a single, double, triple, or home run, right-handed and left-handed hitters perform better when they are up against pitchers of the opposite hand. On average, left-handed hitters fare worse against left-handed pitchers compared to the others. This highlights the prowess and value of left-handed pitchers in baseball. What is interesting is that there is little difference between lefty hitters against righty1 pitchers and righty hitters against lefty pitchers. This simply might be attributed to the sheer amount of right-handed matchups in baseball, suggesting sample size differences that influence the data conclusions. Another hypothesis is that there is simply no significant difference between the two. Regardless, these findings illuminate the evidence behind why baseball players have understood the advantages of platooning early in the game.
Pitcher Performance at Home vs Away
We also wanted to take a look at pitcher performance when playing at a home stadium versus an away stadium. Based on pitcher ERA statistics from the 2020/21 season, the average for away games is slightly higher than home games (ERA: earned run average; the number of runs allowed per nine innings). This may suggest that playing at an away stadium may be a slight disadvantage for pitchers, whether it be pressure from away fans or minor field differences.
More specifically, we can also see that the average total runs given up by pitchers when playing away is slightly higher for all types of runs: single, double, triple, home runs, and walks. The biggest difference is the amount of walks given up, which could potentially further add to the argument of pressure from the away fans.
How has the new foreign substance rule changed pitching?
With the new foreign substance rule the MLB implemented in June of the 2021 season, we were curious about how impactful this new rule was to pitching. The new rule instructs umpires to perform periodic checks on pitchers throughout the game for foreign substance use and bans all foreign substances from being applied to a baseball, excluding rosin. This new rule was enacted because the MLB determined through extensive research that baseballs with foreign substances applied to them, making them sticky, give an unfair advantage to pitchers who use them over hitters and pitchers who do not. This is because the MLB concluded through their research that foreign substances substantially increase the spin rate and movement of baseballs.
To analyze the impact of this rule, we looked at the four seam fastball because it is the most common pitch in baseball and it also heavily relies on spin rate.
First, we looked at the average velocity in miles per hour by month for four-seam fastballs from 2017–2021. It is intriguing that the average velocity of four-seam fastballs in 2021 is consistently higher than the average velocity of the past years, with the exception of October 2018 (only two regular season games were played in October). This trend could possibly be linked to the use of foreign substances. To dive deeper, we should look at the months succeeding the rule change. It is interesting to note that in the months July and August of the 2021 season, the average velocity slightly dips. This could be attributed to the new rule change in June of that season. However, the average velocity steadily increases again in the later months after August and the average velocity is still higher than the previous years, despite the rule change. Since the rule change has not made a significant impact on pitching velocities, we decided to analyze the spin rate of four-seam fastballs.
After looking at the average four-seam fastball spin rate in revolutions per minute by month for the 2017–2021 MLB seasons, we can see that with every season, the spin rate has increased with the exception of 2021. This could be accredited to foreign substance use emerging and becoming more common with every season. However, during the 2021 season, there is a steep drop off in spin rate in the months after May. This drop off in spin rate coincides with the new rule change and it is evident that the rule change has significantly impacted pitchers’ spin rates in 2021. Although, in the months following July, the average spin rate steadily increases while still being lower than the previous seasons.
Conclusion:
In conclusion, several factors influence the performance of a pitcher. After analyzing the distribution of strikeouts by pitch types between Shohei Ohtani and Clayton Kershaw, who are arguably the two most prolific pitchers in recent MLB history, what we found is their most effective pitches are sliders and splitters, respectively. Across all pitches, four-seam fastballs and sliders are the most successful pitch types that result in a strikeout. For Ohtani and Kershaw, going against the grain is what makes them talented and successful. But should all pitchers follow their example? Not necessarily, as it depends on each pitcher’s pitch style and preference, as well as the situation at hand. For instance, in situations where runners are in a scoring position, we discovered that changeups are a valuable option for pitchers to throw as they result in lower hitting and walk rates. To little or no surprise, same-handed matchups tend to favor pitchers, while switch-handed matchups tend to favor batters. Diving even further, left-handed pitchers have an even greater after analyzing the statistics. Another noteworthy factor is how pitchers perform at home vs. away. By looking at their ERA and runs given up, pitchers have a slight advantage when playing at home vs. when they play away. Lastly, a less considered factor, but rising in importance due to new policy changes in baseball, is the effect of foreign substances on pitcher’s performance. The MLB has been recently cracking down on cases in which foreign substances have increased the spin rate and movement of baseballs. After May of 2021, the average four-seam fastball spin rate has drastically dropped, suggesting the new rule change has affected the performance of pitchers’ spin rates. However, since there is a slight variation in the data, other factors, other than the new rule change, may have affected the performance of pitchers. Whether you grew up watching the Dodgers or Angels play in Los Angeles or understand absolutely nothing about baseball, it’s interesting to see just how much goes into being a great pitcher in the MLB.
Data Source & Github Link
Data Source: https://www.kaggle.com/datasets/s903124/mlb-statcast-data?select=Statcast_2021.csv
