Earlier this season, Indians pitchers had an incredible discrepancy between their ERA and their FIP. During the first month of the season, Tribe pitchers had a collective ERA of 4.54, which was among the worst in the American League. Their FIP though (which is based on strikeouts, walks, and home runs allowed) was 3.41, among the very best in the American League.
While ERA and FIP line up league wide (both are 3.81 in MLB this season), it is normal for there to be some difference between the two for individual teams. To have a difference of more than a run is not normal though. The largest difference between the two for any team during the last five years was 0.63, and only three teams during that time had a difference of even half a run.
Drastic differences between the two metrics usually stem from a very low or very high BABIP allowed. A team with a much better ERA probably has a very low BABIP allowed, while a team like the Indians, with a much worse ERA, probably has a very high BABIP allowed. Sure enough, Indians pitchers had a BABIP allowed of .352 during that time, the highest figure of any MLB team, and one that would shatter the American League record of .331.
BABIP is subject to a variety of factors, defense and luck being two of the biggest ones. The Indians had bad defense, and probably some bad luck.
Things settled down a bit in May, but when June began the team still had by far the biggest difference between the two metrics of any MLB team. In the first couple weeks of June, two things happened (well, a lot more than two things happened, but there were two that I'm concerned with here): Giovanny Urshela was called up on June 9 and Francisco Lindor was called up on June 14.
It has been roughly a month since those two came up, overhauling the infield defense. During the last month, the Tribe's BABIP allowed has been just .270. Their FIP has been 3.59, nearly identical to what it was prior to the last month, second best in the American League and very close to their full-season figure. Their ERA though, has been dramatically different from earlier in their year. During the last month, the Tribe ERA has been 3.37, a full .70 lower than it was for the season's first two months.
Are Lindor and Urshela responsible for all of this? Certainly not. Others must have been playing better defense too, and the team's luck has probably been quite a bit better too. It's been a nice mixture of things, and I'm happy for all of it.
FIP has thought Tribe pitchers were among the best in the American League all season. ERA has finally started to agree.