Starting Pitcher GB% Surgers by Mike Podhorzer May 26, 2015 The batted ball distribution metrics, for both pitchers and hitters, are some of the most stable statistics around. A pitcher’s ground ball rate stabilizes after just 70 batters faced, which is basically just three starts. So what this means is that when we see a significant change in a player’s batted ball mix, we have to take it seriously. Let’s take a look at the starting pitcher’s who have enjoyed the largest surges in their ground ball rates and see if we could uncover an explanation. Name 2015 GB% 2014 GB% Diff Michael Pineda 53.2% 39.1% 14.1% Gio Gonzalez 57.9% 44.8% 13.1% Ubaldo Jimenez 54.0% 41.4% 12.6% Shelby Miller 50.3% 39.9% 10.4% Jake Odorizzi 40.1% 29.9% 10.2% Nick Martinez 43.3% 33.6% 9.7% Danny Salazar 43.8% 34.4% 9.4% Drew Hutchison 44.2% 36.1% 8.1% Jeremy Hellickson 44.6% 36.5% 8.1% It’s not enough that Pineda has combined absolutely pinpoint control with a strong ability to induce swings and misses. He has taken his overall skill set to entirely new heights by turning from a fly ball pitcher into a ground ball one. All of his pitches have induced grounders more frequently than in the past and a quick look at his heat maps shows us that he has indeed been working lower in the zone. Health is the only thing holding him back from potentially being a top five or 10 starting pitcher the rest of the way. Gio Gonzalez’s pitch mix is very similar to last season, with the only difference coming from throwing more two-seamers rather than four-seamers. But, he’s thrown two-seamers at similar rates in the past and still hasn’t sniffed this high a ground ball rate. Like Pineda, all of his pitches are generating grounders at higher rates than he typically has, while the move to more two-seamers has helped given the huge disparity in grounder rate it induces versus the four-seamer. Despite continued velocity erosion, Ubaldo Jimenez has rediscovered his ground ball inducing ways of yesteryear. Not since 2009 has he posted a ground ball rate above 50%. Like Gio above, Jimenez is using his two-seamer more often at the expense of his four-seamer, but unlike Gio, the two fastballs have near identical career ground ball rates and are similar again this season. The real difference has been from his slider, which has induced a grounder nearly 67% of the time versus a 39% career mark. Upon his move to Atlanta, Shelby Miller has become quite a different pitcher. He has swapped some four-seamers for two-seamers and thrown significantly more cutters at the expense of his curve ball. Both the two-seamer and cutter are his groundballiest pitches, so this change in mix provides quite the easy explanation. It has helped his skills bounce back, but unfortunately he’s benefiting from an enormous heaping of good fortune. Jake Odorizzi is easy — he’s throwing more of his cutter and splitter/change instead of his four-seamer and slider. His ground ball rate remains below the league average, but at least he won’t be as homer prone as he was in the past. All of Danny Salazar’s pitches, with the exception of his four-seamer, are generating a higher rate of grounders. And according to our PITCHf/x data, his new curve has apparently induced a grounder half the time and a line drive the other half. Of course, those additional grounders haven’t mattered much yet, as his HR/FB rate sits at an inflated 17.9% mark, pushing his HR/9 rate at a career high 1.44. But that’s going to drop, of course, and that 28.6% K%-BB% is going to make him shine.