Sports Reference Blog

As the 2024 season begins, we have made some updates to our Wins Above Replacement calculations on Baseball Reference. You may notice some small changes to figures as you browse the site. As always, you can find full details on how we calculate WAR here.

Biographical Updates
Last summer, we applied some biographical updates to the site, including a few player identification changes where playing records had been found to be credited to the wrong player. This update has correctly re-allocated WAR based on those new player identifications.

2022 Park Factors
Park factors for 2022 have been re-computed to include the 2023 season, since WAR uses a three-year average for park factors when computing pitching WAR. The most significant changes here are the Baltimore Orioles, whose pitching park factor fell from 103 to 100 (where <100 represents a pitcher’s park and >100 represents a hitter’s park), the Cincinnati Reds (fell 110 to 107), and the Los Angeles Dodgers (fell from 103 to 99).

The biggest gainers from these changes were 2022 Dodgers hitters Freddie Freeman, Trea Turner, and Mookie Betts who each gained 0.3 WAR, and Dodgers pitchers Tyler Anderson, Tony Gonsolin, Clayton Kershaw, and Julio Urías, who each saw a 0.3 decrease. These changes all correspond to Dodger Stadium shifting from being considered a hitter’s park to being a very slight pitcher’s park. All other changes to 2022 WAR are smaller in magnitude than these three examples.

New Data From Retrosheet
On Monday, we deployed an update to past box scores, play-by-play, and game logs from Retrosheet, including play-by-play for 3,868 games that previously did not have play-by-play coverage, including full play-by-play coverage of the 1912 season and 66% of the 1913 season, two seasons that previously had no play-by-play coverage at all.

A notable change from this new data is Walter Johnson, whose WAR in 1912 rises by 1.1. The new play-by-play data shows us that Johnson’s 13 relief appearances largely came in high leverage situations. In fact, only two of those appearances had a starting leverage index of less than 1 (indicating below average leverage), and the average starting leverage index was 3.14. For comparison's sake, the highest average starting leverage index in Mariano Rivera’s career was 2.14 in 2012. Since we assume a leverage index of 1 in the absence of play-by-play data, this allowed us to correctly put more value on his relief performance, which is reflected in his increased WAR. 

Biggest Career Movers
Aside from Walter Johnson and the players involved in identification changes, no players experienced a change greater than 1 win.

We’ve highlighted some of the more extreme changes here, but to see full lists of the largest changes to season and career WAR totals, please see the spreadsheet here.

This entry was posted on Tuesday, March 19th, 2024 at 12:16 pm and is filed under Advanced Stats, Announcement, Baseball-Reference.com, Data, Statgeekery, WAR. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.