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23 Jun 2009 |
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Tweet me!| Last week, I discussed the various free ERA estimators out there for our analytical pleasure, and discussed the strengths and weaknesses of each metric. Our own Brian Joura suggested that I take it one step further and look at which pitchers the ERA estimators most disagree on. I thought this was an excellent idea, so that is exactly what I will be revealing to you today. I compiled all the ERA estimators discussed in last week's article for each qualified pitcher, calculated the difference for every pair of ERA estimators, and sorted the list to figure out which pitchers and ERA estimators showed the largest discrepencies. For the tRA and tRA* metrics, I multiplied them by .925 to estimate the tERA and tERA* equivalents. 1. Edwin Jackson, 2.39 ERA xFIP- 4.29 ERC- 2.38 Difference- 1.91 The largest difference in any pair of ERA estimators for one pitcher was between xFIP and ERC for Edwin Jackson. As discussed last week, ERC includes actual hits allowed, whereas xFIP is fielding independent and assumes a league average BABIP. Jackson has benefited from a .260 BABIP, the exact mark that ERC uses in its calculation, which explains part of the discrepancy here. The other huge difference stems from ERC's lack of an adjustment on home runs allowed. Since it uses actual home runs allowed, and does not incorporate current research on HR/FB ratios, Jackson gets credit for his low 5.6% HR/FB ratio, whereas xFIP adjusts this into the 10%-11% league average range (the xFIP is not explicitly divulged, so I am not certain of the exact HR/FB ratio used). Since I sit on the the xFIP side of the fence, I think Jackson is a fantastic sell high candidate. 2. Jered Weaver, 2.53 ERA xFIP- 4.42 ERC- 2.52 Difference- 1.90 Here we are again with an almost identical difference and the same two ERA estimators pitted in battle. Weaver has received almost the exact same type of luck as Jackson above, as he has enjoyed a .261 BABIP and 6.0% HR/FB ratio. However, Weaver is an extreme fly ball pitcher, and since fly balls fall for hits less often than ground balls, it would stand to reason that his BABIP won't increase all the way to league average. That said, I have been trying to sell high on him in my main league, and will continue to do so. 3. Dan Haren, 2.23 ERA tERA*- 3.40 ERC- 1.66 Difference- 1.74 Woah, a 1.66 ERA says ERC?! I bet ERC is Dan Haren's favorite ERA estimator! The difference here is almost entirely driven by Haren's .238 BABIP, as his HR/FB ratio is actually a normal 11.0%. Haren is also probably not getting full credit by tERA* for his splendid 1.2 BB/9, since the metric regresses the component (as well as others) to try to derive a pitcher's true talent level. 4. Jamie Moyer, 6.35 ERA tERA*- 4.72 ERC- 6.42 Difference- 1.70 Since tERA* makes park adjustments, Moyer gets a boost from pitching half his games at Citizens Bank Park, while ERC doesn't care what park he pitches in and makes no such adjustments. Furthermore, like with Haren above, tERA* is interested in Moyer's true talent level, regressing his skill components accordingly. It is unlikely that Moyer is a true 6.35 ERA pitcher, especially given his respectable 2.4 K/BB ratio, so tERA* is probably more in line with that should be expected of Moyer going forward, which of course is still not rosterable, but should make the Phillies and their fans happy. 5. Jarrod Washburn, 3.24 ERA tERA*- 4.75 ERC- 3.09 Difference- 1.66 Washburn gets hurt by tERA*'s park adjustments as Seattle has played as a considerable pitcher's park this year and in season's past. He has also benefited from a 6.8% HR/FB ratio which tERA* probably regresses a bit, thought not all the way to league average like xFIP would. ERC simply leaves Washburn's home runs allowed alone. Washburn has also benefited from a .273 BABIP, which is partly because of the splendid Seattle outfield defense, which tERA* is unaware of. 6. Shairon Martis, 5.13 ERA xFIP- 5.88 ERC- 4.26 Difference- 1.62 .256 BABIP. 7.5% HR/FB ratio. Take your choice, as even with a 5.13 ERA, Martis has been lucky according to xFIP! That is hard to believe, but given the fact that he has actually walked more hitters than he has struck out, it is likely true. 7. CC Sabathia, 3.71 ERA xFIP- 4.54 ERC- 2.93 Difference- 1.61 Sabathia's strikeout rate is way down and it is a big concern, especially since he left his last start with biceps tightness. I wonder if this has been bothering him all season, which could explain the K/9 dip. Anyhow, Sabathia has benefited from a .261 BABIP and 6.6% HR/FB ratio, which has hidden his skills decline for the most part. 8. Kevin Millwood, 2.62 ERA tERA- 5.12 ERC- 3.56 Difference- 1.56 This is the first pitcher on this list where both metrics agreed that the pitcher's current ERA was too low. For every other pitcher, ERC thought that the pitcher had either been unlucky or his ERA was about deserved. Millwood has continued to avoid imploding, thanks to a .263 BABIP and an unsustainably high 85.5% LOB% (strand rate). Both metrics regress LOB%, which explains why they are both higher than Millwood's actual ERA. 9. Nick Blackburn, 3.09 ERA xFIP- 4.95 ERC- 3.40 Difference- 1.55 Blackburn has benefited from a .275 BABIP and 5.9% HR/FB ratio, which explains the difference here entirely. It is amazing to me that a pitcher could post a meager 3.8 K/9, while only inducing a slightly above league average percentage of ground balls, yet still have an ERA of just 3.09. In past seasons, Chien-Ming Wang has proven that a pitcher could succeed with a frighteningly low strikeout rate, but he did that with ground ball rate above 60%. Blackburn's apparent success cannot possibly last with that skill set. 10. Cole Hamels, 4.24 ERA xFIP- 3.16 ERC- 4.68 Difference- 1.52 For the first time on this list, ERC dislikes a pitcher, while its combatant likes him. Hamels has suffered from a 15.1% HR/FB ratio, as the Phillies staff seemingly cannot keep the ball in the park this year. His .355 BABIP is greatly inflated as well, but ERC takes these two numbers at face value, whereas xFIP screams "BUY LOW!", figuring Hamels will see these marks regress toward the league average. Well that's the top 10 largest discrepancies between the free ERA estimators. If you didn't realize it, every single pair of estimators included ERC. I have found that ERC has typically been far off from every other ERA estimator, which is why I completely ignore it and consider it the worst of the free estimators. For the most part, all of the other ERA estimators are remarkably similar, expect for the times when a pitcher has an abnormally low or high HR/FB ratio, at which point the FIP metric will look different from its peers.
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Tags: Edwin Jackson Jered Weaver Dan Haren Jamie Moyer Jarrod Washburn Shairon Martis CC Sabathia Kevin Millwood Nick Blackburn Cole Hamels pitchers luck ERA estimators sabermetrics
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