Michael Fulmer is the defending American League rookie of the year, and he’s showing no real signs of a sophomore slump. That’s good because it means he’s continuing to perform at a high level. It also is good because there was some concern that his rookie success wasn’t sustainable. The basis for that concern was the gap between his ERA and his defensive-independent pitching statistics (“DIPS”). Jeff Sullivan raised the issue late last season:
It sure is tough to trust the legitimacy of Fulmer’s ERA-FIP gap. Certainly at least to this extent. I don’t think he’s demonstrated that he’s “earned” it. You might counter that Fulmer should get more credit, given the Tigers’ defense; they’re 28th in DRS, and 23rd in UZR. But it’s important to remember that defenses don’t play exactly the same every day behind every pitcher. Bad defenses can look good, and good defenses can look bad. As a comparison, think about lineups and run support. The Red Sox are the Red Sox, right? But Rick Porcello has a run-support average of 7.0 runs per nine. Eduardo Rodriguez has a run-support average of 3.0 runs per nine. Baseball’s weird. Just because the Tigers don’t have a good defense doesn’t mean they haven’t had a good defense behind Michael Fulmer.
Fulmer finished last season with an ERA of 3.06, which would have been third-best among qualified AL pitchers had he thrown enough innings to qualify (he was three short), and a FIP of 3.76. Following the general principle that DIPS (such as FIP) are more reflective of a pitcher’s true talent than ERA, Fulmer’s negative ERA-FIP gap suggested that he wouldn’t be able to sustain his low ERA going forward.
In fact, Fulmer’s successful results have continued. Through June 25, his 3.29 ERA places him in the top ten among qualified AL pitchers, and he’s been the fourth most valuable pitcher by fWAR across both leagues. Perhaps even more significantly, he’s doing all this with a positive ERA-FIP gap. Even better, he seems to be doing it without significant alteration to his approach. The only noticeable change I detected there was an increase in velocity, which will be interesting to monitor down the stretch in light of some of the concerns voiced last season about fatigue and endurance.
For context, this table (data pulled from FanGraphs) shows all qualified pitchers currently running positive ERA-FIP gaps:
Viewed this way, Fulmer’s differential doesn’t look all that impressive– it’s only the third-best gap among his own teammates! The point, though, is the trend. Last year, he had one of the worst ERA-FIP gaps, which is what prompted Sullivan’s concern about Fulmer’s potential for future success, and there he is, near the bottom of the list of qualified pitchers from the 2016 season:
In fact, a number of pitchers who finished 2016 with negative ERA-FIP gaps are in the black this year. Of the twenty-nine pitchers currently running positive ERA-FIP gaps, eighteen of them finished 2016 with negative gaps.
(We can get more precise than FIP. Baseball Prospectus’ DRA tells a similar story on Fulmer, whose ERA significantly undercut his DRA in 2016 (3.06 and 3.50, respectively), a differential that also has flip-flopped thus far in 2017 (3.29 and 2.89, respectively).)
These year-to-year swings in ERA-FIP/DRA gaps weren’t what Sullivan was writing about, though. His point simply was that Fulmer’s excellent 3.06 ERA likely was an unrealistic representation of Fulmer’s true talent and that, in the near future, Fulmer’s ERA likely would move in the direction of his FIP. That’s exactly what happened. Fulmer’s having another excellent season thus far, but his ERA is higher than it was last season, just as expected. What’s next? That’s the point of this suddenly meandering post. He’s reversed his ERA-FIP split, suggesting that his ERA’s going to come back down. (In fact, his current 3.08 FIP is almost exactly the same as last year’s 3.06 ERA.)
All of this is about projecting Fulmer’s future performance, and, as helpful as noting positive and negative gaps between a pitcher’s ERA and his FIP or DRA can be, cFIP (which is presented on a 100 “minus” scale, where 100 is average, scores below 100 are better than average, and scores above 100 are worse than average) is the most precise tool available when we want to look into a pitcher’s future. Fulmer’s cFIP marks– 87 in 2016 and 84 so far in 2017– reinforce what his positive ERA-FIP gap suggests. Amidst darkening days for the Tigers, Fulmer remains a bright spot as the team begins its transition toward the future.
Saving Detroit: Tigers in Retrograde – 6/19
Saving Detroit: Fixing Justin Upton – 5/31
Saving Detroit: Soft in the Middle Now – 5/30
Saving Detroit: Reliever Relief, Part 2 – 5/11
Saving Detroit: Reliever Relief – 5/8
Man vs. Machine