Roster Editing Question - Groundball %

[bhrangerfan0809]

I'm in the process of updating rosters for the 2016 season, and one type of editing I'm doing is updating players' ratings based on their performances from the last two seasons. The issue I've come across only happens with a few players - most notably Andrew Miller.

I took the totals from Miller's 2014 and 2015 seasons and inputted the numbers (8 HR, 37 BB, 204 K, 124 IP) after changing his Groundball % to 47 (his average over those two seasons). After I do all of that, the ERA (which I understand to be FIP) comes out around 1.95, which is still higher than Miller's average FIP from those two seasons (1.83). So, I raise the groundball percentage to 48, but then his ERA jumps north of 2.00, and I can only bring it down to the 1.83 range if I increase his GB% to around 75...Can someone tell me why this is happening?

[delv213]

It actually says "Groundout %" not "Groundball %". Miller being a GB pitcher would have his groundout % above the 60% threshold. The guideline I use is someone like Aaron Sanchez for example, has a 55% GB rate as a pitcher according to Fangraphs. His groundballs get converted to outs the majority of the time so his "groundout %" is above 70%. Also coming with that is the fact the game represents that anyone with I believe 58-69% "groundout" in their "pitcher ratings" is recognized as a "GB pitcher" in their profile page to the right of the screen where "Type" is. To get an "extreme GB" type (which he is) in Sanchez's profile his "groundout %" needs to exceed 70%.

Works the same way with anything below 50%, anything between 41-49% makes the pitcher a "flyball pitcher". Marco Estrada as another example has an extremely high flyball rate compared to GB%, he still has groundballs converted to outs so but to get him to give up more flyballs and become an "extreme flyball" pitcher (which he is) his "groundout" rate has to become less than 41%, so I have him set at 40%.

Hope that helped! I discovered this not too long after I started editing and I naturally assumed it was groundout % too.

[delv213]

Another thing I forgot to write was since you understand advanced statistics, you must take into account parks are going to influence the amount of homers that your pitcher gives up, which does effect FIP to a small degree and ERA to a larger extent. You must increase or decrease the "movement" in the editor of a pitcher to LHBs/RHBs or "groundout rate" to manually offset the prediction on the "resulting stats" as that predicts what his stats would be in a neutral ballpark against a regular team. A guy like Masahiro Tanaka for example, who's got a strong GB% in 2014 and 2015 would be less likely to give up a homer inside a more neutral park like Comerica Park (Detroit) than in Yankee Stadium (New York) so you have adjust accordingly to give him slightly more favorable predicted stats in that sense because he is a better pitcher outside Yankee Stadium but is going to get punished a bit anyways because of the ballpark he's pitching in the majority of the time.

You also shouldn't need to edit anything that would result in an improved strikeout numbers as my experience with editing is that is generally accurate when compared to the predicted stats and that should be more influenced by the batters the pitcher faces.