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:
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: