Lefty Grove weighs in at 36%. I didn't realize what tremendous run support Grove got from the Athletics in the early 30's.

It may be a shade behind Seaver and Maddux, but it doesn't change my opinion that Lefty was The Man among post-1920 pitchers. What it does do is make me appreciate how great Seaver and Maddux were. Man, that 35%+  improvement over team performance is one upscale neighborhood.