Introduction

As a Phillies fan, it was an exciting (and exhausting) three games in Arizona during the current Phillies/Diamondbacks “best of 7 games” NLCS playoff series to decide the National League representative in the 2023 World Series. The Phillies had bullpen meltdowns in both Games 3 and 4 to lose those two games by close margins. They needed a strong starting performance from their ace Zack Wheeler in Game 5 Saturday night and he delivered, leading the Phillies to a 6-1 win.

Zack Wheeler has pitched very well in Games 1 and 5 of this particular playoff series and I thought it would be interesting to explore his pitching, hopefully to gain a better understanding of how he has been effective. We use Statcast data scraped using functions from the baseballr package in this exploration.

Pitch Types and Outcomes

Let’s begin by looking at the pitch types that Zack threw in the two games (October 16 and October 21). Here I display a frequency table of the pitch type for each game. Generally, in these games Zack threw about 55% four-seamers, 12% sinkers, with the remaining split between curveballs, sliders and sweepers. It is interesting that Zack threw a greater percentage of curveballs and sliders in the second October 21. I suppose this change was intentional based on the experience from the October 16 game.

  game_date 4-Seam Fastball Curveball Sinker Slider Sweeper
 2023-10-16              45         6     11      2      17
 2023-10-21              55        12     10      8      14

What were the outcomes (variable description in the Statcast dataset) of these different pitch types? From this table, we see Zack has good control of his four-seamer — only 23% (23 out of 100) of his fastballs are balls. In contrast, higher percentages of his other pitches are balls. Note from the table that 15 of his fastballs resulted in swinging strikes; also he had some swing-and-miss for all of his different pitches.

             description 4-Seam Fastball Curveball Sinker Slider Sweeper
                    ball              23         9      8      3      10
            blocked_ball               0         2      0      0       0
           called_strike              18         1      1      2       8
                    foul              20         1      3      2       2
                foul_tip               1         0      1      0       1
           hit_into_play              23         0      3      0       6
         swinging_strike              15         3      5      3       3
 swinging_strike_blocked               0         2      0      0       1

Pitch Locations

To learn more, we display the location of all of Zack’s pitches for each pitch type. The color of the point corresponds to the outcome. From the top-left display, we see Zack throws many of his four-seamers middle and high in the zone. In contrast, he tends to throw his curveballs low out of the zone. Similarly, many of his sweepers are located low and to the right (catcher’s view) — I suspect these are thrown primarily to right-handed hitters. (I did check — 24 of 31 sweepers were thrown to right-handed hitters.) All but one of the sinkers (20 out of 21) are thrown to left-handed hitters and they are located low and outside of the zone.

The Count

One reason why Zack is so successful is that he tends to be ahead in the count. I construct a frequency of the count across all of the plate appearances. I define the pitcher advantage to be the number of current strikes minus the number of current balls — a positive value indicates the count favors the pitcher. Here I graph the current number or pitches for all counts against the pitcher advantage where the size of the label corresponds to the frequency. (Large labels correspond to larger frequencies.)

What do we see?

• Zack tends to get a strike on the first pitch — 0-1 (larger label) is much more common than 1-0 (smaller label).
• After two pitches, he is equally likely to be at 0-2 or 1-1 — the 2-0 count is rare.
• After three pitches, he is more likely to be at 1-2 than at 2-1 — he did not face a 3-0 count in these two games.
• 2-2 counts are relatively common, but 3-1 and 3-2 counts are rare.
• In summary, Zack tends to enjoy pitcher counts in a PA.

Quality of Balls Put Into Play

Let’s explore the balls put into play against Zack. First I display a scatterplot of the launch angle and exit velocity of alls balls in play, where the color of the point corresponds to a hit (green) or out (red). The two large points are the ones which resulted in home runs. Zack tended to get many grounders (launch angle smaller than 10 degrees) and popups. A couple of hits were bloop singles with launch speeds between 70 and 80 mph.

The quality of the ball put into play depends on the current count. One way of measuring the quality of the BIP is the estimated batting average which is based on the launch variable values. Below I construct a dotplot of the estimated BA against the count for all of the BIP against Zack. It is interesting that the estimated BA values are low for the pitcher counts 2-2 and 0-2. Ten of the BIP had estimated BAs exceeding 0.5 — of these high BA values, 3 were on a 1-1 count, 2 were on a 0-0 count and 2 were on a 2-1 count. This is a small sample, but it suggests that the batters might do better with a BIP on a pitch early in the count. (This might explain why some hitters swing on the first pitch.)

Comments

We could do more exploration on Zack’s pitching. For example, we could explore how the characteristics of his pitches compare with other starters, look at his strike and walk rates, and see if he tends to exhibit fatigue. Baseball Savant has an interesting “Pitcher Visualization” page where you can learn about Zack’s pitching tendencies for the 2023 season. Zack is known to possess an excellent four-seam fastball with good control and he complements the fastball with a variety of other types of pitches.

This brief exploration shows off many of Zack’s strengths.

• Zack is a strike thrower and tends to be ahead in the count. This helps keep his total pitch count low, it helps to get more swings and misses, and leads to poor quality of the balls in play.
• He tends to throw his four-seamer for strikes and throw his off-speed pitches out of the zone to induce the swing and miss.
• Since he throws five different pitches, he has the ability to adjust the frequency of his pitch types by the batters he faces and the game situation.

Hopefully in a future post I will have the opportunity to explore Zack’s pitching in the 2023 World Series.

R Notes

I have put all of the R work for this post inside a quarto document found here on my Github Gist site. Assuming you have all of the packages installed, you can reproduce all of this work by rendering this quarto document. Here are the useful packages.

• I use the baseballr package to scrape the Statcast data from Baseball Savant.
• I use the dplyr package for some data manipulation and ggplot2 for the graphical work.
• The janitor package is helpful for creating the cross-tabulations.