Zack Greinke In ‘The Peripheral Disconnect’

Pitchers whose ERAs and estimators disagree are extremely interesting to analyze. On one hand, their signature run prevention mark might appear toward the top of leaderboards while the underlying numbers aren’t as fruitful. On the other side of the spectrum are pitchers like Zack Greinke, who, as Chris Cwik pointed out yesterday, has a vast disconnect between his ERA and FIP. In fact, it’s been that way since the first week of May when he came off of the disabled list.

His 2.63 FIP and 2.12 xFIP suggest that the newly-minted Brewers starter has been one of the best in the league. But Greinke’s actual 5.63 ERA is closer to the bottom than the top, and is three runs higher than his adjusted marks. One of the more popular stats here is E-F, a sortable number that measures the gap between ERA and FIP. Pitchers with a large separation are expected to regress in some fashion, because it is incredibly rare for anyone to finish with a huge disagreement between those two data points.

I thought about taking that concept a bit further and calculating the difference between ERA and xFIP, since the latter metric is a better predictor of future earned run average than its predecessor. This makeshift ‘E-X’ number would be measurable from 2002-now, and it piqued my curiosity to see which pitchers had the largest such gaps in that span.

Granted, the separation in Greinke’s numbers is unlikely to remain as substantial as the season wears on, but he was more of an introductory device here as opposed to a player being compared — obviously it wouldn’t be accurate to compare his numbers through two months to those amassed over full seasons for other hurlers.

Looking at pitchers whose ERAs exceeded their xFIPs since 2002, here are the guys with the biggest ERA-xFIP deltas:

Carlos Silva (2008), 1.88 E-X
Silva’s numbers looked terrible above the surface: a 4-15 record and a 6.46 ERA. Beneath those numbers, however, was a 61 percent strand rate and .342 BABIP. He managed a K/BB above 2.0 without striking anyone out, and induced grounders on 44 percent of his balls in play. His ERA estimators by no means suggested he was an upper echelon pitcher, but rather that he was closer to league average than the bottom of the pile. The 1.88 delta between his 6.46 ERA and 4.58 xFIP is the largest in this span.

Ricky Nolasco (2009), 1.83 E-X
Can’t say his name is shocking to see here. If I were to have polled you prior to revealing the list, Nolasco and Javier Vazquez’s names were likely to pop up. Nolasco tossed 185 innings in 2009 with a 5.06 ERA, despite a 9.5 K/9, 2.1 BB/9, 3.35 FIP and 3.23 xFIP. Unlike Silva, the estimators here suggest that Nolasco was one of the best in the league, and his 4.3 WAR in 2009 bears that out.

Unfortunately, nothing has really changed for Nolasco, who continues to be one of the more frustrating pitchers in baseball to follow, and potentially the Vazquez of this generation.

Nate Robertson (2008), 1.73 E-X
His numbers almost directly mirror those of Silva: a 6.35 ERA and 4.62 xFIP in 168 2/3 innings. Robertson struck more batters out but issued walks at a greater frequency. This issue seems to have plagued him forever, as he has a career .304 BABIP, 68 percent strand rate, 5.01 ERA and 4.45 xFIP.

James Shields (2010), 1.63 E-X
Finally, an example of a guy who actually met the expectations of his xFIP in the following season. Last year, Shields put up an ugly 5.18 ERA, but struck out 8.3 batters per nine in the tougher American League, while producing a 4.2 K/BB ratio. He finished the season with a 3.55 xFIP, and while his numbers are regression-bound this season (in the other direction, given his .256 BABIP and 82 percent strand rate), his peripherals have largely remained the same and his performance is more in line with what those underlying numbers suggest.

Jose Lima (2005), 1.63 E-X
Once again, we alternate the terrible made to look closer to league average with the ‘meh’ made to look solid. In this case, however, we’re looking at the equivalent of putting lipstick on a pig. Lima might not have been as bad as a 6.99 ERA suggests, but his 5.36 xFIP wasn’t exactly inspiring. He makes the top five because even someone with peripherals as unsightly as his couldn’t be expected to sustain a 7.00 ERA pace.

What stood out when looking at the 870 pitcher-seasons with 150 innings included in the span was how so many of those with an ERA at least a run greater than their xFIPs fell in line with Silva and Robertson as opposed to Nolasco and Shields. Of the 42 whose E-X was 1.00+, the weighted averages included a 5.49 ERA, 4.54 FIP and 4.22 xFIP.

The only pitcher in the span with a sub-4.00 ERA to also have a delta of one or more runs is Curt Schilling, back in 2002, when he pitched a 3.23 ERA, 2.40 FIP and 2.22 xFIP in 259 1/3 frames.

Perhaps this speaks to the notion that better pitchers are less likely to see large disconnects between their ERA and estimators. Because of their skillsets, it is less likely for a fluky BABIP or strand rate to influence run-prevention. For every Cole Hamels‘ 2009 there are likely double-digit Cole Hamels‘ 2010 replicas. Either way, there is no way that Greinke’s current three-run separation persists without his shattering the E-X record. Considering he has an 11.6 K/9 and 1.7 BB/9, it seems much more likely that his ERA improves than it does that his estimators will materially suffer.