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Friday, October 17, 2008
Starter, reliever or swingman?
What I’m going to say here only applies to 2008, but likely applies for the last decade. There were 1.07 innings per relief game, and 5.81 innings per start. If someone like Justin Masterson has 9 starts and 27 relief appearances (36 games in all), with 88.3 innings, how many innings can we estimate that he pitched as a starter and reliever? If we give him the league averages of 1.07 and 5.81 for his 27 and 9 games respectively, we get a total of 81.2 innings. We are missing 7.15 innings, which we prorate to his 36 games (0.2 innings per game), and conclude he pitched 1.27 innings in relief and 6.01 innings as a starter. That gives us a total of 34.3 in relief and 54 as a starter. In reality, he had (gulp) 34.3 and 54.
Honestly, a purely lucky pick on my part. I was just going through the team pages and looked for someone who was used as a swingman. I checked the 4 teams last in the playoffs, and Masterson was the best candidate. I’m sure it won’t be this close (perfect!) in most cases. The reason I bring this up is because Justin looked at Reds pitchers and decided to put a player as a starter or reliever. But since the replacement level for the starter is a .380 win% (128% of league average ERA) and for reliever it’s .470 (107% of league average ERA), then I don’t like the idea of an either/or. This way, using my process, you can count Masterson as 39% reliever and 61% starter and give him a replacement level baseline of .415 win% (120% of league average ERA).