I recently wrote about Statcast measures that were highly correlated with power metrics, such as HR/FB and ISO. The research confirmed that several Statcast measures could be useful tools for identifying undervaled power sources. One factor I ignored in that analysis was pull rate, but in taking a belated look at it, I found that one of the apparently strong relationships gets notably weaker when we control for a hitter’s pull tendencies.
In general, exit velocity on flyballs and line drives turned out to be strongly correlated with ISO for hitters with at least 150 batted ball events in 2018. However, when you isolate the top 10 percent of the sample in terms of pull rate, the relationship is still meaningful, but it’s not quite as strong. That could have implications for how we view two of last season’s top power hitters, Jose Ramirez and Alex Bregman.
Typically, hitters who launch airborne balls with high average exit velocities generated more extra-base power, but for the 32 hitters who compiled pull rates of at least 48.2 percent, that relationship mattered less. Pull rates have been associated with higher ISOs, and in 2018, a pull rate above the 90th percentile nearly guaranteed an ISO above the major league average of .161. Within this extremely pull-heavy group of 32 hitters, only five failed to post an above-average ISO. As the table shows, the R-squared between average exit velocity on flyballs and line drives fell from 0.50 for all hitters with at least 150 plate appearances to just 0.34 for the subset of hitters at or above the 90th percentile in pull rate. Meanwhile, the other relationships tested experienced less dramatic changes after winnowing out the approximately 90 percent of hitters with the lowest pull rates.
|Correlation Between:||All hitters with 150+ BBE||Hitters with 150+ BBE and 48.2%+ Pull%|
|Barrels/BBE % and HR/FB||0.67||0.61|
|Barrels/BBE % and ISO||0.67||0.58|
|EV FB/LD and HR/FB||0.58||0.61|
|EV FB/LD and ISO||0.50||0.34|
An extremely high pull rate did not nullify the relationship between ISO and average exit velocity on flies and liners, but to some extent, it overshadowed the impact of exit velocity. Both Ramirez and Bregman were a part of the top 10 percent in pull rate in 2018, so it is curious that both were among 20 hitters whose ISO was more than 40 points higher than what it was expected to be based solely on the correlation between ISO and average exit velocity on flies and liners. In fact, the 93-point positive gap between Ramirez’s actual ISO (.282) and his expected ISO (.189) was the second-greatest in the entire pool of 332 hitters studied, exceeded only by Max Muncy’s 95-point gap.
Of the 20 hitters with disparities of more than 40 ISO points, 11 hit flyballs for an average distance of at least 330 feet, but neither Bregman (329 feet) nor Ramirez (323 feet) were among them. Another two hitters — Tyler White and Didi Gregorius — had lopsided home/road splits that reflected favorable home park conditions for hitting home runs. The power output of two others — Eduardo Escobar and Joc Pederson — is still something of a mystery, and pending more investigation, both should be considered ISO regression candidates. The remaining five hitters — Bregman and Ramirez, plus Evan Gattis, Christian Villanueva and Alen Hanson — were among the top 10 percent in pull rate. This is not a consequential fantasy development for Gattis (who figures to be a late-rounder in most format), Hanson (who will probably go undrafted in the vast majority of leagues) and Villanueva (who will play in Japan in 2019).
That leaves Ramirez and Bregman among the potential ISO overachievers, and their extreme pull rates are a plausible explanation for why their ISOs were higher than their average exit velocities on flyballs and line drives would suggest they should have been. Of the 35 hitters in this study with ISOs above .240 in 2018, 27 averaged at least 94 mph on flies and liners, but Bregman (.246 ISO, 93.4 mph) and Ramirez (.282 ISO, 92.4 mph) fell short. Pulling the ball at an extremely high rate helped to put them on a par with other top power hitters.
Given Bregman’s and Ramirez’s reliance on a pull-heavy approach, should we be concerned about them being at risk of experiencing pull rate regression in 2019? The year-to-year correlation of pull rate since 2015 is fairly strong with an R-squared of .464, but that doesn’t mean we should expect pull rates to remain stagnant. Over that span, the average year-to-year change (absolute value) in pull rate was 3.5 percentage points. From 2017 to 2018, Bregman increased his pull rate from 42.6 to 48.4 percent, so it’s conceivable he could regress towards both his own mean (44.6 percent) and the major league mean (40.3 percent in 2018). Ramirez increased his pull rate from an already-elevated 46.3 percent in 2017 to 50.0 percent in 2018. Fantasy owners have to be prepared for the possibility that both hitters will have less extreme pull tendencies in 2019.
For Ramirez, that could mean more doubles and fewer homers, though he may need to reverse an increase in IFFB% to approach his 2017 total of 56 doubles. Bregman did increase his average exit velocity on flyballs and line drives by 1.6 mph from 2017 to 2018, so even with some pull rate regression, it is unlikely he will backtrack all the way to the .191 ISO he posted in ’17. As he will be entering his age-25 season, we could even see Bregman hit with even greater velocity, and maybe fully compensating for any decrease in his pull rate.
If early mocks like the 2 Early Mocks and the Pitcher List Experts Mock are any indication, Ramirez will frequently be one of the first three players taken, and Bregman will be a late-first rounder. Their apparent reliance on pulling the ball to generate more power should not be a reason to deeply discount either player, but building your 2019 team around them may involve more risk than there seems to be at first glance. Using the third overall pick on Ramirez seems especially risky, when Francisco Lindor, Nolan Arenado and J.D. Martinez offer similar upside with less potential for volatility.
Al Melchior has been writing about Fantasy baseball and sim games since 2000, and his work has appeared at CBSSports.com, BaseballHQ, Ron Shandler's Baseball Forecaster and FanRagSports. He has also participated in Tout Wars' mixed auction league since 2013. You can follow Al on Twitter @almelchiorbb and find more of his work at almelchior.com.