Jeff Locke and Rick Porcello are two pitchers with large gaps between their xFIP and ERA. How you value them depends largely on your faith in defense-independent pitching theory. Porcello sports a 3.27 xFIP but a 4.28 ERA. While his ERA- is a pedestrian 105, his xFIP- is an excellent 82. Porcello ranks 42nd among qualified pitchers in FIP WAR at 2.1 while his RA9 WAR ranks 57th at 1.5. Locke on the other hand has posted an unsightly 4.09 xFIP but a sparkling 2.47 ERA. His ERA- is a sterling 68 while his FIP- is 101. Based on FIP WAR, Locke ranks 58th at 1.4 while RA9 WAR puts him at 13th with 3.9. RA9 or “actual run prevention” says Locke is a real ace, the 5th best pitcher in his league, and Porcello is a slightly below average pitcher. xFIP says Porcello is an excellent pitcher, while Locke is merely a middling arm.
In order to understand the difference between Porcello and Locke, I dug deeper into their peripheral stats. Both have similar strikeout rates, with Locke at 18.1% and Porcello, who does not have the luxury of facing his own kind, at 17.8%. While Porcello has a 5.1% walk rate, Locke’s 11.3% is well above the MLB average of 8.0%. Porcello has been victimized by the long ball, as his 13.5% HR/FB rate is the highest since his rookie year, and two full points above his career average of 11.5%. On the other hand, Locke has managed to suppress home runs, as he has posted a 6.8% HR/FB rate. Some of this can be attributed to their respective home fields, as Comerica has a home run factor of 101, while PNC Park’s home run factor of 92 makes it the 3rd most difficult park to hit a home run. I would be wary of attributing any home run avoidance skills to Locke, as he allowed 9 home runs in 51 innings with the Pirates over 2011-12. ZiPs has him projected for a 9.9% HR/FB rate over the remainder of the season. Locke has also enjoyed an excellent LOB%, as his 82.2% is currently 5th in the majors among qualified starters while Porcello’s 69.5% is 74th. MLB average LOB% is 73.3. While Locke’s LOB% seems destined for regression (ZiPS projects it to be 69.0% ROS), a below-average LOB% may be part of Porcello’s profile, as his 69.5% is actually a career-best number.
However, the biggest reason for the ERA separation between Porcello and Locke is the defense behind them. Both Porcello and Locke are groundball pitchers, and their higher than average contact rates make them heavily dependent on their fielders. Porcello’s GB% of 57.2 is 2nd highest in the MLB, while Locke’s 53.3% is 8th highest. The Tigers have a team BABIP% against of .300 which ranks 6th highest in the MLB, while the Pirates are 2nd lowest at .271. Porcello’s BABIP of .313 is 13th highest among qualified starting pitchers, while Locke’s .261 is 75th. The following hand-picked GIFs illustrate the difference.
Porcello works with this:
(He doesn’t actually but I imagine the Tigers’ ballboy was inspired by their defense)
And Locke has this:
(From Forbes to Federal)
The difference in their defenses has contributed to the Tigers’ pitchers underachieving their xFIP, and the Pirates beating their xFIP. While the Tigers pitching staff has a league-best 3.38 xFIP, their team ERA is 6th-best at 3.57. The Pirates have the 5th-best xFIP at 3.67, but a team ERA of 3.09 that leads the league by a wide margin, with the Braves next at 3.24. Put in other terms, the Tigers ERA is 106% of their team xFIP, while the Pirates ERA is 84% of their team ERA. Rick Porcello’s ERA is 131% of his xFIP, while Jeff Locke’s ERA is 60% of his xFIP.
After an analysis of the Locke and Porcello’s defense-independent stats and their defense-dependent stats, I thought it would be interesting to see what combining the best and worst of both worlds would be. The following chart is Porcello’s actual ERA and then his ERA calculated by multiplying his xFIP by the “Pirates Factor.”
|ERA||xFIP||Pirates Factor||“What if” ERA|
And this chart shows Locke’s actual ERA and then his ERA calculated by multiplying his xFIP by the “Tigers Factor.”
|ERA||xFIP||Tigers Factor||“What if” ERA|
I know, it’s a back-of-the-napkin calculation. xFIP doesn’t adjust for park and league factors, and Porcello’s LOB% probably wouldn’t jump to the Pirates’ team average of 77.1%. Nevertheless, its an interesting example of the difference that defense, park, league, and luck factors can have on a pitcher’s ERA over the course of a season. If Porcello pitched for the Pirates, he would probably be widely recognized as a very good pitcher, while if Locke pitched for the Tigers, he would most likely look average or worse. A change of scenery could have a big impact on either pitcher. But hey, who knows, maybe the recent acquisition of this guy can help Porcello look a little better.
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