Astros’ Run Expectancy & Pitch Framing

My Two Topic Tuesday. If you have read my articles, you already know that RE24 is one my favorite stats for evaluating the performance of hitters and relief pitchers. With the season nearing its conclusion, I will look at the Astros’ best players based on RE24, and how they compare to other players at their position. My second topic investigates whether umpires’ favorable calls are related to catcher pitch framing. At the end of this article I will provide another update on the Astros’ playoff odds.

Run Expectancy (RE24)

The RE24 stat tells us how well a player performs in increasing the probability of scoring a run in each plate appearance. In some ways, this statistic is better than offensive stats like wRC+ and Runs Above Average, which are based on “averages” of how much particular batting events are worth.

I’ll repeat my previous explanation of RE24. RE24 measures the change in run expectancy based on the 24 base-out states. (The 24 base-out situations refer to the combination of runners on base and outs—for example, bases loaded with 2 outs is one of the 24 base out states, and has an average run expectancy of 0.736 runs scored.) The actual change in run expectancy produced by a player is compared to league average run expectancy for each of the base-out states. Unlike the normal offense stats such as wRC+ or wOBA, RE24 takes into account the game situation and includes skills like advancing the runner and avoiding double plays.

Below are the Astros’ five best RE24 performers and their ranking among all MLB hitters at their positions.

RE24 Runs Above Avg. / Ranking at Position / Comparable Players

1. Yordan Alvarez RE24: 58.4 Runs / No. 2 Among DH / Ranked Between Ohtani and Judge
2. Kyle Tucker RE24: 38.3 Runs / No. 4 Among RF / Acuna, Betts, and Judge are 1, 2.3
3. Alex Bregman RE24: 34.6 Runs / No. 1 Among 3b / Bregman is 7 runs above Devers
4. Chas McCormick RE24: 31.8 Runs / No. 3 Among CF / Rodriguez and Carroll are 1, 2
5. Jose Altuve RE24: 23.4 Runs / No. 4 Among 2b / 49% fewer PA than No. 3 Semien

The notable aspect for these high MLB RE24 rankings is that Alvarez, McCormick, and Altuve all have considerably fewer plate appearances than their peers. Consider that Alvarez has 52% more RE24 runs than the next highest Astros’ player—yet he accomplished that in 42% fewer PA than the number 2 hitter (Tucker). McCormick has 36% fewer PA than No. 1 CF Julio Rodriguez.

I also like RE24 as a measure of relief pitcher performance. It is a measure that is more precise than WHIP, recognizes the difficulty of coming in with runners on base and avoids the inherited runners issues that may bias reliever ERA.

Two Astros relievers stand out on the RE24 statistic. Bryan Abreu is No. 4 among all relievers in RE24 (at least 50 innings). Hector Neris is No. 12 on the MLB reliever RE24 leaderboard.

Relationship Between Umpire Scorecard and Catcher Framing

Pitch framing refers to the ability of the catcher to catch the ball from the pitcher in a way that maximizes the chances of getting a strike called. Various different methods are used to attempt to estimate this effect. The Astros do not rank well on those metrics. For the statcast method, the Astros rank 29th (next to last). If you believe the metric, both catchers—Maldonado and Diaz—are poor at pitch framing. Maldonado is -13 and Diaz is -3.3. If you want to compare Diaz to Maldonado on a comparable inning basis, multiply Diaz’s number by three.

Before I go further, there are a number of caveats that make the catcher pitch framing metric a rough estimate, at best. As Fangraphs’ glossary states, the framing metric does a good job of measuring “extra strikes,” but it is “problematic” at assigning credit to individual catchers. We know that the umpire, pitcher, and catcher can all influence framing stats, but assigning credit to each party is somewhat arbitrary. The glossary states: “ there is no way to distinguish whether the catcher received the ball well or if the umpire is calling an unusually large strike zone during that specific game.”

The Umpire Scorecoard is a site which tracks the accuracy of umpires’ ball/strike calls and calculates whether the “misses” are called as a net favorable or unfavorable to each team. The Astros have the fourth worst ranking in favorable calls (-11). My question is whether the Umpire Scorecard calculation of favorable calls is relate to the team’s pitch framing.

I compared teams’ favorable pitcher calls based on Umpire Scorecard, with team catcher framing stats based on Fangraphs’ defensive stat page. The results were eye opening (at least for me).

Correlation 0.79

R-Square 0.63

A correlation of 0.79 is quite good for most types of baseball data. The R-Square is supposed to tell us how much the variation in one variable is “explained” by the variation in a second variable. For instance, if you believe that pitch framing is influencing umpire’s calls, this might be interpreted as “pitch framing explains 63% of the variation in umpire favorable pitch calling.”

Stepping back, maybe I should have expected a reasonable amount of correlation. After all, both metrics (Umpire Scorecard and Pitch Framing) are using pitch f/x to identify strikes that should have been called balls, and balls that should have been called strikes.

Although I started this exercise to determine whether pitch framing explains unfavorable umpire calls against each team’s pitcher, it’s also possible that the cause and effect goes the opposite direction. The Astros and other teams with negative umpire favorability rankings for pitching also tend to receive negative favorability calls on their batters. Does this indicate a subtle level of umpire bias? Who knows. And a more likely scenario is that teams with negative rankings on both the batter and pitcher side were assigned umpires who were particularly inaccurate on a given day. If a team randomly receives an above average or below average number of inaccurate umpire calls, that is likely to affect the measured effectiveness of pitch framing. So, I can’t eliminate the possibility that the umpire accuracy explains the pitch framing results.

My takeaways? First, perhaps the Astros should place a renewed emphasis on pitch framing in the organization. Second, automated umpire calls or a ball/strike challenge system can’t get here fast enough.

Brief Update on Playoff Odds

I have gotten into the habit of updating the Fangraphs Playoff Odds in each article. Despite the disappointing loss on Monday, the Fangraphs model still sees the Astros in the cat-bird’s seat. The Astros have a 66% chance of winning the division and a 95.5% probability of making the playoffs.