Impact of eWin Error
Baseball Player Won-Loss Records
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Impact of the Recent Correction of an Error in the Calculation of eWins



Player won-lost records were updated on January 12, 2018 to fix a fairly significant error in the calculation of (context-neutral, teammate-adjusted) eWins and eLosses.

Briefly, eWins and eLosses were being calculated without controlling for ballpark effects. Rather than averaging across every play within a particular ballpark, as I intended to do (and as I described in my book, I was mistakenly averaging across all plays within a particular league-season.

This article looks at the impact of correcting this error on results for specific players and teams.

Todd Helton
The impact of this change is most dramatic on players and teams which play in extreme ballparks (in terms of their impact on run scoring). Certainly, the most dramatic ballpark over the past 25 seasons has been the home of the Colorado Rockies. The best player to have played his entire career as a member of the Rockies was Todd Helton. It stands to reason, then, that the player whose record was most impacted by this update was probably Todd Helton.

Here is the impact of this update on Todd Helton's career record.

pWins pLosses pWOPA pWORL eWins eLosses eWOPA eWORL
Previous
246.0208.26.5
23.9
264.5201.918.6
36.5
Corrected
246.2208.36.5
24.0
250.9201.312.4
29.8


Obviously, that's a big change. For most players, however, the change is not nearly so large.
Top and Bottom Batting Teams
Prior to this update, here were the top and bottom 10 teams in terms of net (context-neutral) batting wins for whom I had calculated Player won-lost records.

Net Batting Wins
Top 10 Teams
          Net Batting Losses
Top 10 Teams
Team Season eWins eLosses           Team Season eWins eLosses
1New York Yankees1927123.4102.3
21.1
1Houston Astros196395.3112.2
-16.9
2Cincinnati Reds1976129.9109.6
20.3
2Seattle Mariners201096.9113.6
-16.7
3Brooklyn Dodgers1953127.5109.6
17.9
3Oakland Athletics197994.1110.0
-15.9
4Cincinnati Reds1965127.2110.1
17.2
4Washington Senators I194890.4106.1
-15.6
5Colorado Rockies1996125.7109.2
16.4
5Houston Astros196494.1109.6
-15.5
6Brooklyn Dodgers1951126.4110.1
16.4
6New York Mets196598.7114.1
-15.5
7Boston Red Sox2003130.4114.2
16.2
7Detroit Tigers200294.5109.7
-15.2
8Boston Red Sox1950124.9109.1
15.8
8Baltimore Orioles195596.2111.0
-14.7
9Colorado Rockies1997126.6110.9
15.7
9Seattle Mariners201196.1110.8
-14.7
10New York Yankees193199.784.4
15.3
10San Diego Padres196994.0108.5
-14.5


Obviously, there's a high correlation between the run-scoring environment of the ballpark and which list these teams are on. This is most evident by the presence of the 1996 and 1997 Colorado Rockies, which were good hitting teams but probably not historically so.

Having corrected the treatment of ballpark effects, the top and bottom hitting teams are shown next.

Net Batting Wins
Top 10 Teams
          Net Batting Losses
Top 10 Teams
Team Season eWins eLosses           Team Season eWins eLosses
1New York Yankees1927119.498.3
21.1
1Washington Senators I194890.7107.3
-16.6
2Cincinnati Reds1976129.3110.1
19.2
2New York Mets196596.0111.9
-15.9
3Brooklyn Dodgers1951126.4109.1
17.3
3Arizona Diamondbacks200497.5113.1
-15.6
4New York Yankees1931101.884.6
17.2
4Houston Astros196496.4112.0
-15.5
5New York Yankees1930100.784.0
16.7
5Seattle Mariners2010101.6117.0
-15.5
6New York Yankees1936102.586.0
16.5
6Minnesota Twins199995.8111.0
-15.2
7New York Yankees1939112.596.3
16.2
7Miami Marlins2013100.7115.5
-14.8
8New York Yankees2009135.5119.7
15.8
8Oakland Athletics197996.2110.9
-14.7
9Brooklyn Dodgers1953124.7109.0
15.7
9Houston Astros196399.5114.0
-14.6
10New York Yankees1953115.3100.1
15.2
10Philadelphia Athletics194389.4103.5
-14.1


That looks much better to me. And, frankly, I'm embarrassed that it took me so long to figure out that something was so obviously wrong.

Miscellaneous Players
Finally, here are changes in pWins and eWins over positional average and replacement level for a dozen players chosen somewhat randomly.

Original Corrected
Player pWOPA pWORL eWOPA eWORL pWOPA pWORL eWOPA eWORL
Barry Bonds 60.490.758.5
88.3
60.390.760.290.3
Carlton Fisk 21.239.922.4
40.6
21.340.121.139.3
Mike Mussina 29.651.329.2
50.6
29.651.328.349.6
Carl Yastrzemski 18.050.922.3
56.1
17.950.818.851.7
George Brett 22.847.519.9
44.8
22.747.619.744.7
Wade Boggs 18.639.819.8
41.5
18.539.818.840.4
Eddie Murray 18.744.910.4
35.2
18.745.010.736.0
Paul Molitor 19.847.315.0
42.2
19.847.415.442.5
Toby Harrah 14.633.418.5
37.3
14.733.518.637.4
Luis Tiant 20.840.411.9
30.9
21.040.313.932.4
David Wells 17.438.413.9
35.0
17.438.313.234.1
Tony Perez 14.837.711.1
33.3
14.837.811.033.1


My apologies for this error. I hope that you will continue to enjoy Player won-lost records.



All articles are written so that they pull data directly from the most recent version of the Player won-lost database. Hence, any numbers cited within these articles should automatically incorporate the most recent update to Player won-lost records. In some cases, however, the accompanying text may have been written based on previous versions of Player won-lost records. I apologize if this results in non-sensical text in any cases.

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