Playoff WPA and the Astros

As the Astros head into the World Series, familiarize yourself with the Baseball-Reference.com stat: Championship Win Probability Added (cWPA). This form of the well known WPA stat, measures each player’s contribution of win probability toward the World Series. A theoretical +100% or -100% is equivalent to a world series game won or lost. Players on each team in the playoffs has accumulated cWPA during each playoff series.

For WPA, everything is about timing. cWPA is about offense or pitching at a critical moment that increases or decreases the probability of a championship. Some people criticize WPA because they contend a run at the beginning of a game should count the same as a run in the 9th inning; yet WPA gives more value to the actions in the late innings of a close or tied game. But in the playoffs, cWPA makes some sense. In a relatively short series, pivotal events—tide turning actions even—can decide whether the team wins the playoff series and goes to the World Series.

Let’s look at the Astros’ top offensive players in cWPA during the ALCS.

1. Alvarez 13.41%
2. Castro 6.48%
3. Altuve 5.39%
4. Brantley 1.92%
5. Correa 0.76%

Now for the Astros five worst offense cWPAs during the ALCS.

1. Tucker -8.87%
2. Bregman -4.08%
3. Maldonado -2.86%
4. Diaz -2.19%
5. McCormick -1.17%

And, just for fun, here are the Astros five best pitcher cWPAs during the ALCS.

1. Graveman 6.32%
2. Valdez 5.36%
3. Javier 3.52%
4. Maton 3.29%
5. Stanek, 2.32%

Some observations:

• Alvarez’s cWPA shows you why he deserved the ALCS MVP.
• Castro’s cWPA is pretty amazing, considering that he had only 3 at bats. (Castro’s OPS is over 2 in those three at bats.) And this shows that the ability to target a pinch hitter for critical moments in the game can result in overwhelming cWPA results. Given the importance of pinch hitting in the NL ballpark, perhaps this shows the benefit of holding a player on the bench to pinch hit in the big game moments.
• Players’ overall batting stats don’t necessarily correlate with high cWPA. For instance, Tucker produced a good .885 OPS in the ALCS, but he also produced the worst cWPA. Altuve had a poor .589 OPS in the ALCS, but he still managed to produce the third best cWPA. Altuve had a great 1.1 OPS in the ALDS and produced the fourth best cWPA in the ALDS.
• It doesn’t appear that cWPA is necessarily repeatable. In the ALCS, Tucker and Bregman are at the bottom of Astros’ cWPA results, but in the ALDS, Bregman is no. 1 and Tucker is no. 3 in cWPA. The link for cWPA in the ALDS is here.
• Graveman’s and Maton’s high cWPA demonstrates that timing is everything for relief pitchers.
• Oh, by the way, turning to the Red Sox cWPA in the ALCS is interesting. Remember when Enrique Hernandez looked like an all world hitter? Hernandez was so hot in the first three games that game thread commenters wanted to walk him for the rest of the series. It turns out that Hernadez ended up with a negative cWPA (-0.52). As far as cWPA goes, sometimes the most important thing is how you end the series rather than how you start it.

So, who do you think will be the Astros’ cWPA leaders for offense and pitching in the World Series?