To put it simply, it’s hard to pitch at Fenway Park if you are a lefty starter. Looking at the park’s dimensions, you may point to the vast right field and the depth to dead center as reasons why it may favor the pitcher.
But one glance at left field where the hulking Green Monster stands, and all of a sudden it’s a right-handed hitter’s paradise. A 350-foot pulled fly ball that results in an out in almost every other stadium clanks off the wall for an easy double. It’s no wonder that Fenway Park ranked fourth in 2017 among MLB stadiums in park factors for doubles (1.156 where 1.000 is neutral), via ESPN.
Overall in 2017, right-handed hitters had an advantageous runs factor of 102 (where 100 is neutral) at Fenway Park, ranking 12th in MLB. Move over to Progressive Field, where Kluber calls home, and that plummets to 93, ranking 28th in MLB, according to Baseball Prospectus.
As a left-handed starter, it’s typical for opponents to stack their lineup to be righty-heavy. Thus, Sale was met with 719 plate appearances from right-handed hitters and just 132 from left-handed hitters. That overwhelming split difference is nowhere near the one that Kluber had to face, matching up against same-sided righties 410 times and lefties 367 times.
To summarize, Sale was dealt a disadvantageous hand, facing more competition of the unfavorable sidedness and pitching at a home stadium that favors such a matchup.