Groundballs and the Overall Picture by Matthew Carruth February 19, 2010 I have seen people claim that a pitcher’s ground ball rate is not a useful piece of information because grouping pitchers by it shows no meaningful difference in runs allowed. FIP is comprised of a pitcher’s strikeouts, free passes (walks plus hit batsmen) and home runs. Based on the last few posts the data seems to indicate that strikeouts and free passes are not meaningfully effected by a pitcher’s ground ball rate and home runs decrease. A scatter plot bears out the expected result. Instead of artificially grouping pitchers, a full trend line points to a pitcher’s ground ball rate being a useful piece of information, even on its own. It is not just FIP though but actual runs scored follows the same trend. In conclusion from the previous five pieces here is a a list of variables that appear to have no meaningful deviation as a pitcher’s ground ball rate increases: Home run rate per non-groundball Overall strikeout rate Overall walk rate Slugging percentage on line drives in play. And here is a run down of what I consider the be the key results found for what does happen as a pitcher’s ground ball rate increases: Slugging percentage on fly balls in play increases. Overall slugging percentage on non-ground balls increases. Less pop ups are allowed. More runners reach via error. Fewer home runs are hit. Their FIP goes down. Their RA goes down.