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:

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.