Who Were the Luckiest and Unluckiest Starting Pitchers in May?

After a dominant first month with some unsustainable peripherals, Ervin Santana was supposed to come crashing back down to reality in May. It didn't happen, though.

With Memorial Day officially in the rearview mirror and the calendar telling us it's June, we are forced to actually consider certain trends as more legitimate instead of dismissing them because of a small sample size. Sure, there are four more months remaining in the 2017 MLB regular season, but two months of data can tell us who is having a good year and who isn't.

As we found out last month, some of a starting pitcher's statistics don't tell the whole story with regard to how they're actually performing. Jeremy Hellickson was among the league leaders with a 1.80 ERA by the end of April, but a lot of his peripheral stats showed that his success wasn't built to last if certain trends didn't change.

Lo and behold, he's done a complete about-face over the past month, and his 4.45 ERA so far this year looks quite a bit different than it did just a month ago.

As sample sizes start to stabilize (or get closer to stabilizing), we want to figure out which starting pitchers experienced more bad luck than the average, and who ended up being rather fortunate over the past month.

On the pitcher’s mound, the most common statistics we see thrown around include win-loss record, ERA and WHIP, but we all know there’s more to individual performances than that.

With that in mind, we’re going to compare their ERA to their Skill-Interactive ERA (SIERA).

According to FanGraphs, SIERA attempts to measure the underlying skill of a hurler. Unlike FIP and xFIP, SIERA doesn't ignore balls put in play, and it also attempts to give a more accurate picture as to why certain pitchers are better than others. A good SIERA is just like a good ERA -- the lower the better.

For this exercise, we'll be looking at qualified starting pitchers from the past month, as determined by FanGraphs, which spans a total of 95 hurlers.