This article is part of our The Saber's Edge series.
The public's disdain for flyball pitchers can be traced to two things: Common Sense and xFIP. Common sense tells us that a hitter is extremely unlikely to hit a home run on a groundball. The more a pitcher can generate groundballs, he will have better results.
Besides the age-old common sense, my previous boss, Dave Studeman, created xFIP a little more than 10 years ago. xFIP is an ERA estimator which uses strikeout, walk and flyball rate. The data mainly points to pitchers having a higher home runs rate as they allow more flyballs.
Heads up, I am going to stop right now using any mention of flyball rate. I find baseball full of too many stats already. Instead of memorizing cut-offs of flyball and groundball rate, I just use groundball rate. If you want to convert groundball rate (GB%) to flyball rate (FB%) use FB% = 80%-GB% with the other 20 percent going to line drives.
xFIP works for most pitchers with more than 75 percent of all pitchers having a groundball rate less than 40 percent and 87