Given some of the recent discussions on how stats are related to luck, I wanted to look at how the luck of various pitchers compares, using the difference between ERA and FIP as a crude measure of pitchers' luck. I also wanted to look at the difference between starters, middle relievers, and closers. Just to establish some sort of basis, I took the top ten players in Quality Starts, Holds, and Saves, as well as anybody else with the same number of those as the tenth guy. I then calculated "Luck" as their ERA-FIP, divided by 9 to get Per-Inning Luck, multiplied by IP to get Total Luck, and then summed everyone's Total Luck, divided by Total IP, and multiplied by 9 to get a Weighted Average Luck for each group (snazzy acronym suggestions will be accepted). One caveat: by taking the top pitchers of each group, presumably I'm also getting some of the luckiest pitchers, so their WAL will presumably be better than average for their position.
Combined, the starters have pitched 1,513 innings. They range from the slightly unlucky Weaver (-0.15 ERA-FIP) to the very lucky Hudson (1.93 ERA-FIP). As a corps, the starters have a WAL of 0.75, suggesting that these guys are moderately lucky.
Combined, these player have pitched 350.2 innings. Joba has been hideously unlucky, with a -3.07 ERA-WIP, while the luckiest is Daniel Bard's 1.25. On a whole, the middle relievers have a WAL of -0.27, so they are unlucky overall. However, removing just Joba from the equation would shift the WAL to 0.07.
These players have pitched a total of 554.2 innings. Nunez and Neftali are the only unlucky pitchers, with Nunez being at -0.76. Kevin Gregg is perfectly balanced, and the luckiest closer is Rivera, at 1.22. As a whole, relievers are somewhat lucky, at 0.44 WAL.
Given the limits of this look, it appears that the current top starters are luckier as a whole than the top closers, who are luckier than the top middle relievers. Given time over the next few weeks, I'll try to look at some of the worst in each category to see if the pattern is consistent that starters>closers>middle relievers for luck.