The Pulled Flyball Revolution by Al Melchior August 22, 2019 Not so long ago, when it came to pull-heavy power hitters, there was no equal to Brian Dozier. Based on developments currently unfolding this season, the genre could explode in 2020. Back in 2016, Dozier was unique among major league hitters in his ability to pull flyballs at an extremely high rate consistently. Among hitters who launched at least 100 flies in both 2015 and 2016, Dozier was the only batter to exceed a 35 percent pull rate on flyballs in both seasons. He essentially lapped the field, surpassing a 40 percent rate in both campaigns. Then Dozier was the only hitter to pull off the feat in both 2016 and 2017. In 2018, there were four hitters who eclipsed a 35 percent pulled rate on flyballs, though Dozier was not among them, and none had a rate as high as 33 percent in 2017. So far this season, only Randal Grichuk is on pace for back-to-back seasons with a rate above 35 percent, though José Ramirez (35.5 percent in 2018, 34.9 percent in 2019) is awfully close. Over the last several seasons, there have been a handful of hitters every year who have exceeded a 35 percent flyball pull rate, but no one has matched Dozier’s consistency. That’s not to say, however, that there isn’t a year-to-year correlation in flyball pull rate. So far this season, there is an R-squared of .30 between hitters’ rates this year and last year (min. 100 flyballs). It’s a highly significant correlation (p < .0001) yet also the weakest correlation in at least four seasons. The year-to-year correlation for flyball pull rate matters, because pulled flies typically get hit for far more extra-base power than other flies. This season, hitters have posted a cumulative 1.140 ISO on pulled flies and a .346 ISO on all other flies. It also matters because there are currently 10 hitters with at least 100 total flyballs and a flyball pull rate of at least 35 percent this season. All but three of these hitters (Dozier, Grichuk and Edwin Encarnación) have surged to the upper reaches of this leaderboard with a year-to-year increase of at least eight percentage points. Across 2016, 2017 and 2018 combined, Grichuk was the only hitter to achieve a 35 percent flyball pull rate by increasing that rate by at least eight percent from the previous season. The flyball pull rates for the other seven hitters are displayed in the table below. Each of these hitters is doing something that has been exceedingly rare in recent years, but Max Kepler is really doing something special. He has tacked on 94 points to his ISO despite not adding power (as measured by average exit velocity on flyballs and line drives) or hitting more flies (his flyball rate has dipped slightly from 46.2 percent to 46.0 percent). Kepler has gone from having normal pull tendencies to extreme ones, raising his flyball pull rate from 24.1 percent to 43.8 percent. 2018-19 Pull Rate, ISO and EV FB/LD Hitter 2018 FB Pull% 2019 FB Pull% 2018 ISO 2019 ISO 2018 EV FB/LD (mph) 2019 EV FB/LD (mph) Max Kepler 24.1% 43.8% 0.184 0.278 93.8 93.2 Hunter Renfroe 29.7% 41.8% 0.256 0.297 97.4 95.2 Paul DeJong 30.7% 40.1% 0.193 0.208 93.4 92.3 Todd Frazier 29.5% 37.7% 0.176 0.183 93.8 91.6 Matt Olson 23.9% 36.8% 0.207 0.274 97.4 96.6 Eduardo Escobar 23.8% 35.3% 0.217 0.257 90.8 90.9 Marcell Ozuna 25.9% 35.0% 0.153 0.239 94.9 97.4 Exit velocity data are from Baseball Savant. Hunter Renfroe, Paul DeJong and Todd Frazier have used stronger pull tendencies to combat decreases in average exit velocity on flies and liners (EV FB/LD). Marcell Ozuna’s bounceback season has been fueled by both an increase in EV FB/LD and a sharp increase in his flyball pull rate. Matt Olson and Eduardo Escobar are hitting with a similar EV FB/LD in 2019 as they did in 2018, but both have upped their power game with more pulled flies. Escobar’s power output was an enigma last season, and it continues to be this year, even with his lofty 35.3 percent pull rate on flyballs. He is slugging .528, but according to Baseball Savant, his xSLG is still just .457. With the 33-year-old Frazier in the decline phase of his career and Escobar somehow getting the better of xSLG in back-to-back seasons, it’s reasonable to look for both players to decline in their power output in 2020. However, with flyball pull rates having a strong year-to-year correlation, we should expect Kepler, Renfroe, DeJong, Olson and Ozuna to have similar power numbers next year (assuming they sustain them over the final weeks of 2019). It’s especially encouraging to see that the hitters who have experienced the greatest year-to-year increases in flyball pull rate over the previous three seasons have generally maintained those gains in the following season. There have been a total of 33 hitters over that period who have increased their rate by at least five percentage points from one season to the next, and only nine of them (27.3 percent) regressed by at least five percentage points the following season. One of the hitters who didn’t regress — Eugenio Suárez — is actually following up an increase of 6.2 percentage points last season with an increase of 6.5 percentage points this season. If we limit the pool of these hitters to those who have had a year-to-year flyball pull rate increase of at least eight percentage points — matching the magnitude of change for the seven hitters featured in the table above — we have a total of 16 cases. Only three (18.8 percent) regressed by at least five percentage points in the following season, and the remaining 13 hitters kept their flyball pull rate within a range of plus-or-minus five percentage points from the previous year. Five of those hitters further increased their rate just one season after they had already boosted it substantially. If this trend persists, there may be only one or two players from the table who will give back the bulk of their gains in flyball pull rate from this year. With the new ball creating power gains for countless players this year, it’s not always easy to separate out the sustainable improvements from the passing ones, but Kepler, Renfroe, DeJong, Olson and Ozuna are looking primed to carry this year’s power numbers into next year. Acknowledgement: The inspiration for looking at year-to-year correlations in flyball pull rate came from seeing Tom Tango’s recent tweets which showed the year-to-year relationships for average exit velocity and launch angle. Note: The season-to-date data presented here are for games played through Wednesday, Aug. 21.