As we have heard, and I have written about, Monica Abbott is now the highest paid women’s athlete in a team sport. Though she signed a 6-year, $1 million contract, is she as good as her salary says she is?
According to data collected from Abbott’s 2015 season in the National Pro Fastpitch (NPF) league, she is really, really good. So good, in fact, that no one comes close to her numbers. To start, she pitched just over 90 innings for the season, had a 13-1 winning record, and an ERA of .31. To say that she was the best pitcher in the 2015 league would be an understatement. The next best pitcher from that season with roughly the same amount of innings pitched, was Cat Osterman who had an ERA of 1.35.
Abbott, though, did not always best Osterman in ERA. In 2014, Osterman posted a 0.56 ERA while Abbott’s mark was 1.50. In 2013, though, Abbott was once again the “best” with an ERA of 0.92 (while Osterman’s mark was 1.06). Then in 2012, Osterman’s 0.72 topped Abbott’s ERA of 1.06.
All of these numbers beg the question: who is better? Let's answer this question by first focusing on the 2012 season.
Once again, at the end of the 2012 season Cat Osterman was seen as the best pitcher in the league. She ended the season with a 0.72 ERA, far better than anyone else in the league- including Monica Abbott. These stats, though, are misleading. Voros McCracken argued in 2001 that statistics like ERA and won-loss records are poor measures of a pitcher’s performance. This is because these stats are not just about the pitcher; obviously a pitcher cannot win a game by herself. The problem with ERA may be less obvious. Pitchers are certainly charged with earned runs, but as McCracken noted, pitchers and the defensive players around the pitcher work together to get hitters out and prevent runs. So ERA is not just about the pitcher.
Rather than focus on ERA, McCracken argued we would be better off focusing on defensive independent statistics like strikeouts, walks, home runs, and hit batters. Because these statistics are much more under the control of pitchers, these statistics are more consistent across time. Consequently, McCracken developed the Defense Independent ERA.
JC Bradbury laid out the basic methodology in The Baseball Economist.* Specifically an individual pitcher's ERA is statistically connected to the defensive independent factors (again, strikeouts, walks, hit-by-pitch, and home runs) and then a defensive dependent measure like Hits per Ball in Play (HperBIP)– or [(Hits – Home Runs) / (Outs + Hits – StrikeOuts – Home Runs)].
The results indicate that 89% of the variation in a pitcher's ERA is explained by the defense independent factors and HperBIP. In addition, these results can be used to construct a pitcher's Defense Independent ERA, or a measure of a pitcher's performance that is independent of the players around the pitcher. Though Osterman had a better ERA statistic, taking the Defensive Independent ERA into consideration, Abbott ended the season with better numbers. Check out the table below:
Monica Abbott: ERA = 1.06; Defensive Independent ERA = 1.31
Cat Osterman: ERA = 0.72; Defensive Independent ERA = 1.65
These numbers tell us the Osterman had a better defense around her. But the defensive independent stats all favored Abbott. Per 7 innings the stats for each pitcher were as follows
Strikeouts: Abbott = 10.58; Osterman = 9.39
Walks: Abbott = 1.78; Osterman = 1.86
Hit-by-pitch: Abbott = 0.28; Osterman = 0.43
Home run: Abbott = 0.33; Osterman = 0.43
Yes, Osterman was good. But Abbott – across all four stats – was better. And the same story is told across each pitcher's career. Osterman's Defensive Independent ERA for her career was 1.36. At the end of the 2015 season, Abbott's mark was 1.20.
As McCracken and Bradbury note, the Defense Independent ERA is much more consistent over time and that tells us that this measure is actually a better reflection of the pitcher’s actual value. Using the DIPS ERA, one can see the true value that a pitcher adds to a team, ignoring the other eight defensive players that contribute in their own way.
Looking directly at Monica Abbott, she has a .92 Defensive Independent ERA for the 2015 season. This is interesting, to me at least, because that means that she is a good pitcher overall, but her team is great overall. Without a solid defense behind Abbott, she wouldn’t have the numbers that she has today. However, that is applicable to all pitchers.
Now that we know Monica Abbott has a higher Defensive Independent ERA than a regular ERA, we can truly compare her pitching ability to other well-known pitchers. Jennie Finch, one of the most famous softball players of all time, also played on and off in the NPF from 2005-2010. In her 2005 season, in which she would pitch the most innings out of all of her seasons, she ended with a 1.43 Defensive Independent ERA. This mark is quite similar to her career mark of 1.49.
So who is the greatest? The top three pitchers in NPF history are clearly Abbott, Osterman and Finch. And when we separate all three pitchers from their defense, it appears Abbott – the highest paid women in professional team sports – comes out on top!
This article utilizes statistics reported originally by the National Pro Fastpitch league, the Ladies League has data on Runs Created and Defensive Independent ERA for every hitter and pitcher in NPF history (2004-2015). We hope to continue to update this data going forward.
* Bradbury's method to calculate Defensive Independent ERA was applied to NPF data by Dave Berri. This analysis will be posted at the Ladies League in the future.
You can follow the author of this article on Twitter at @CamiMathews27.
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