Introducing pWin: A Better Pitcher Decision Statistic (Part 3 of 3)

Introducing pWin: A Better Pitcher Decision Statistic (Part 3 of 3)


In the first post of this series, I introduced a new way to calculate pitcher Wins and Losses based on the WPA they accumulate in a game: the pWin/pLoss statistic. In the second post, I used Johnny Cueto’s 2015 season as a case study to tweak the stat. Now I’d like to sum up as well as look at a few extreme historical examples.

First, let’s fully define the pWin/pLoss statistic:

The “pWin” is given to the pitcher on the winning team with the highest WPA in that game. In the case of a tie between 2 or more pitchers, the first tiebreaker is the most innings pitched, and the second tiebreaker is the fewest runs (earned, unearned, or inherited) allowed.

The “pLoss” is given to the pitcher on the losing team with the lowest WPA in that game and who allows at least one run (earned, unearned, or inherited) to score. In the case of a tie between 2 or more pitchers, the first tiebreaker is the least innings pitched, and the second tiebreaker is the most runs (earned, unearned, or inherited) allowed.

All in all, I would not claim that this statistic is perfect by any means, but I think it does a much better job of crediting the proper pitchers with wins and losses.

A few objections I’d like to address.

First, some might argue that using WPA is too confusing for fans to follow. However, even though the traditional Win statistic has been used for decades, I’ll bet most casual fans don’t understand why Ohlendorf or Diaz received W’s for facing just one batter. Also, baseball fans are getting more and more sophisticated when it comes to statistics: just a few years ago OBP and SLG were considered esoteric stats for only the most die-hard stat-head, and now they are displayed on many broadcasts alongside more traditional stats. Finally, it would be easy for a broadcast to simply keep track of the WPA and display it on the screen at various times throughout the game.

Another argument against this stat is actually the argument that the whole “pitcher decision” stat, no matter how it is determined, is worthless. After all, wins and losses are team statistics, not individual ones. And this is a valid argument. However, I would argue that pitcher Wins and Losses have been part of the game since the beginning, and can – if properly calculated – reflect a pitcher’s enormous contribution to a team’s wins and losses. So I would not want to throw out pitcher Wins and Losses, but rather improve it make it more meaningful.

Before I finish, I thought it would be interesting to check out a few more historical games to see if the pWin/pLoss system could right some historical wrongs (or if they would create any). Using Baseball Reference’s Play Index, I first searched for games in which the losing pitcher amassed the highest WPA.

Dodgers vs. Reds, September 15, 1941 (Dodgers win 5-1 in 17 innings)

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In this game Paul Derringer pitched 15(!) innings, giving up 3 runs. For this herculean effort, he was tagged with the L in spite of accumulating 1.162 WPA – tied for the highest ever for a losing pitcher. Looking more closely, we see that two of those runs were scored when Joe Beggs was on the mound – Derringer was taken out in the 16th inning after giving up a home run and two singles. Beggs allowed those two runners to score, and eventually he gave up two more of his own, making it 5-0. The Reds scored one in bottom of the 17th, but that wasn’t enough to save Derringer from being tagged with possibly the most unjust “L” in history. However, the pLoss clearly goes to Beggs, who had a -0.066 WPA for the game – a full 1.228 less than Derringer.

Next I wanted to see who had the lowest WPA ever for a winning pitcher. Again, Play Index to the rescue:

Phillies vs. Braves, July 23, 1964 (Phillies win 13-10 in 10 innings)

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One of the worst instances of the traditional Win statistic is when a reliever blows a save and then ends up with the W. So he is rewarded for failing to do his job – makes sense, right? This game is the most extreme example of that.

Hall of Famer Jim Bunning (future U.S. Senator from Kentucky) didn’t have a great start for the Phillies. He totaled -0.325 WPA by giving up 5 earned runs in 2 innings of work. Fortunately for him, his team was able to score a lot of runs that day. But look closer at the pitcher stats for the Phillies: Jack Baldschun, who totaled a staggering -0.862 WPA for the game, received the W for his “hard” work. How did that happen?

When Baldschun entered the game in the bottom of the 8th, the Phillies were winning 8-6 and there were two on with no one out. At this point, the Phillies had a 65% chance of winning. He quickly got the first batter out to increase the odds to 77%. Then the wheels fell off. By the time the inning was over, the score was 9-8 Braves and the Phillies only had a 15% chance of winning. He pitched another inning and gave up another run, for a total of 4 runs scoring on his watch.

However, it was Baldschun’s good fortune that the Phillies scored 5 runs while he was the pitcher of record, so by the traditional means, he was the “Winner.” None of the Phillies pitchers that day were much to write home about, but the pWin goes to Dennis Bennett, who closed the day for the winning team (in the pWin/pLoss system, a pitcher who gets the traditional “Save” can also get the pWin – but I consider Save stat close to useless, so that doesn’t really bother me).

So these are the two most extreme cases of pitchers receiving ill-deserved decisions, and I’m sure there are many more out there.

I think the pWin/pLoss statistic does a better job of calculating pitcher Wins and Losses than the traditional system. I’ll continue to look at this way of calculating pitcher pWins and pLosses to see if it has any major flaws or ways to improve it, but it is my hope that pWins and pLosses gives fans a more useful way to quickly see which pitcher most contributed to a team’s victory or loss.