For no reason at all: Pitchers with the highest batting averages against on balls in play — that is, batting average against, minus home runs and strikeouts — over the past five years (minimum 600 IP):
Just four of the fifteen pitchers have an ERA+ better than 100.
As is sometimes misstated, a lot of a pitcher’s batting average on balls in play is luck and defense, but some is his own skill. Johan Santana’s batting averages against on balls in play — .278 BAbip for his career — are routinely lower than his team’s defense would imply. Mike Pelfrey’s BAbip are routinely higher (.314 career), and thus he is #13 on this list. There’s A LOT of randomness at work, but it’s not ENTIRELY randomness. Johan Santana is actually better at preventing hits on balls in play than Mike Pelfrey. You can see that the list above is populated with the sort of pitchers you might imagine get hit pretty hard, and I don’t think that’s just a function of chance.
That said, as this chart shows, a lot of BAbip is a pitcher’s defensive help. Good defenses will turn more balls into outs than bad defenses, and bad defenses will turn more outs into hits than good ones. The Pirates have been a bad defensive club for five years. The top three pitchers on that list have spent a lot of time pitching for those Pirates. This is probably not a coincidence.