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Bruce Chen had the magic going on as Royal in 2010 and 2011. He had two of his better run prevention seasons, posting ERA's of 4.17 and 3.77. People pointed out the luck may not last and it didn't last season when his ERA jumped to 5.07. It is just possible his 2012 was the season where (bad) luck was involved and his 2010 and 2011 were closer to what we should expect out of him.
The sabremetric way of telling if a pitcher is "lucky" or not is to see how his ERA compares to his ERA estimators:
| Season | BABIP | LOB% | ERA | FIP | xFIP | SIERA |
| 2010 | 0.275 | 74.3% | 4.17 | 4.54 | 4.79 | 4.74 |
| 2011 | 0.278 | 75.1% | 3.77 | 4.39 | 4.68 | 4.63 |
| 2012 | 0.304 | 69.7% | 5.07 | 4.73 | 4.62 | 4.34 |
As it can be seen, Bruce outperformed his ERA estimators in 2010 and 2011. In 2012, his ERA was slightly above his estimators. The key to having an ERA below the estimators is a low BABIP and therefore a higher left-on-base percentage (LOB%). Bruce seems to have an ability to suppress his BABIP.
Over the last couple of days, Bill Petti and I have been looking at how pitching to the edge of plate helps a pitcher's performance. What we have found it is pitchers who throw a larger percentage of pitches on the plate's edge (I will call Edge%) have better results. The news is not really ground breaking, but the extent of the results are. In the heart/middle of the plate, the average BABIP is .310 and a 14% HR/FB rate. Pitches on the edges have a .289 BABIP and a 10.5% HR/FB.
Chen has exceeds the league average value (~16%) in Edge% on a yearly basis.
Season: Edge%
2010: 17.7%
2011: 18.0%
2012: 17.3%
His Edge% values are by far the best of any pitcher on the staff. A pitcher's Edge% correlates decently from season to season, so Chen is likely to see a high Edge% again and likely see his ERA drop below his FIP in 2012.
Besides Chen, here on the values from some other Royals pitchers.
| 2012 | 2011 | 2010 | |||||||||
| Name | Edge% | Heart% | Outside% | Edge% | Heart% | Outside% | Edge% | Heart% | Outside% | ||
| Luke Hochevar | 15.1% | 35.2% | 50.1% | 15.4% | 34.7% | 50.3% | 15.2% | 35.5% | 49.8% | ||
| James Shields | 14.1% | 29.7% | 56.4% | 15.9% | 34.5% | 50.0% | 14.9% | 35.5% | 49.8% | ||
| Ervin Santana | 14.3% | 34.2% | 52.0% | 15.4% | 34.2% | 50.6% | 14.6% | 34.5% | 51.2% | ||
| Jeremy Guthrie | 16.5% | 32.3% | 51.6% | 16.3% | 33.7% | 50.3% | 16.7% | 32.8% | 50.9% | ||
| Wade Davis | 14.6% | 33.7% | 52.0% | 17.2% | 33.1% | 50.1% | 16.5% | 35.5% | 48.3% | ||
| Bruce Chen | 17.3% | 35.4% | 47.6% | 18.0% | 34.8% | 47.6% | 17.7% | 36.6% | 46.0% | ||
| Felipe Paulino | 16.3% | 34.2% | 49.6% | 15.1% | 35.6% | 49.5% | 14.4% | 34.5% | 51.2% | ||
| Danny Duffy | 16.3% | 36.0% | 49.1% | 16.4% | 36.6% | 47.5% | |||||
| Will Smith | 14.5% | 35.8% | 50.3% | ||||||||
| League Average | 15.6% | 33.2% | 51.6% | 15.8% | 33.6% | 51.0% | 15.9% | 33.8% | 50.7% | ||
| Greg Holland | 13.8% | 33.1% | 54.1% | 14.8% | 33.4% | 53.1% | 11.3% | 36.6% | 54.1% | ||
| Kelvin Herrera | 15.1% | 34.5% | 51.4% | 18.8% | 34.4% | 46.9% | |||||
| Tim Collins | 14.7% | 36.0% | 50.4% | 13.1% | 34.0% | 53.9% | |||||
| Aaron Crow | 14.5% | 32.4% | 54.1% | 12.8% | 32.1% | 55.5% | |||||
| Louis Coleman | 14.1% | 33.6% | 53.1% | 15.8% | 32.9% | 52.1% | |||||
| Everett Teaford | 14.6% | 37.6% | 48.6% | 16.7% | 36.2% | 48.0% | |||||
| Mitch Maier | 37.5% | 37.5% | 25.0% | 12.5% | 37.5% | 50.0% |
Thoughts
- Mitch has the top Edge% of any pitcher in 2012.
- Shields' lower than league average numbers worry me a bit. His huge home (3.33 ERA) and away (4.54 ERA) may point to the Trop really helping him.
- The only starters, besides Chen, with above league average values are Paulino and Duffy and the crafty old veteran, Guthrie.
- Herrera is the only reliever who is even close to being league average, but throwing to the heart of the plate is less of a concern for hard throwing relievers. Their extra velocity allows them to get away with more mistakes across the middle of the plate.
Bruce Chen looked to be lucky by having a lower ERA than his ERA estimators. It now seems like he has the talent to throw strikes near the edge of the plate where it is hard to hit. After losing a bit of the magic in 2012, it is time to see if he can bring it back in 2013.