|About the stats|
Over the course of his career, Jerry Koosman pitched 3,839 innings and made 1,052 plate appearances. Koosman was worth 53.7 Wins Above Replacement (57.0 as a pitcher and -3.3 as a hitter) and 20.5 Wins Above Average (24.0 as a pitcher and -3.3 as a hitter).
After adjusting for length of schedule, catchers, and relief pitchers, the 53.7 WAR becomes 54.8 adjWAR. Then, WAA is adjusted by ignoring negative seasons (thus, truly capturing a player’s peak seasons) and making similar adjustments for catchers and relief pitchers. After these adjustments, the 20.5 WAA becomes 28.1 adjWAA.
Then, the adjWAR and adjWAA are combined, but with extra weighting given to adjWAA. This gives Koosman 105.4 wWAR. wWAR is then converted to Hall Rating. A Hall Rating of 100 represents the Hall of Stats borderline (similar to OPS+ or wRC+, where 100 represents league average).
Jerry Koosman has a Hall Rating of 99, making him close to the Hall of Stats borderline—but still on the outside.
Want even more detail about the formula? See the About page.