In this very early baseball season, any player can have some legitimate Hall of Fame numbers. Take, for example, Cleveland Guardians’ rookie left fielder Steven Kwan, who reached base safely 15 times in his first four games, an MLB record. Or Nolan Arenado, who boasts a ridiculous 1.337 on-base plus slugging (OPS) as of Thursday, April 21.
While these wild stats are enjoyable, small sample sizes — where luck and randomness come into play — are, of course, the culprit. It often seems as though you must either dismiss advanced stats as bogus or praise them as the only way to evaluate a sport, but there ought to be a happy medium where we can appreciate the ridiculous early-season returns without taking them as gospel.
Let’s take a look at how we can measure luck in baseball and see if any players are due for regression to the mean.
Baseball is different from many other sports because of its finite set of outcomes. When a batter steps to the plate, they can walk, strikeout, get hit by a pitch, or hit a single, double, triple or home run. Because of this — and a large sample size — baseball can measure “luck” more accurately than other sports.
Let’s kick off this discussion with one key statistic in measuring a batter’s ability: weighted on-base average (wOBA). Former MLB data scientist Sam Sharpe nicely described this unique stat.
“In short, wOBA measures offensive value of players by weighting outcomes (HR, BB, 1B etc.) by their run value. Compared to BA and SLG, wOBA more accurately represents a hitter’s contributions to run scoring and thus his overall offensive value,” Sharpe said.
Not all hits are valued the same, and wOBA helps to measure a player’s general offensive contribution per at-bat by recognizing the value variation between the different ways one can reach base. However, a player’s wOBA depends on factors they cannot control — like large gusts of wind, lucky bounces off of third base or weird hops off the infield dirt.
Here is where expected weighted on-base average (xwOBA) comes into play. Unlike wOBA, xwOBA is completely context neutral and tries to guess which outcomes are most likely given the exit velocity and launch angle of the contact and the speed of the player. It’s a debate as to how much control a batter has over where the ball goes beyond these metrics, such as the aforementioned game conditions or luck.
In other words, wOBA demonstrates how well a player is hitting, whereas xwOBA predicts how well a player should be hitting.
One player whom luck has certainly not favored in the early parts of the season is Joey Gallo. The polarizing Bronx bomber is still largely considered an above-average player despite his high strikeout totals (led the MLB in strikeouts with 21 in 2021).
As of April 21, Gallo has batted a pathetic 0.200 wOBA. However, he has also produced a rather impressive 0.364 xwOBA. Gallo thus possesses a large discrepancy between xwOBA and wOBA at a whopping 0.164.
That’s odd, isn’t it? What’s the deal? Is something wrong, or is he just unlucky?
The shift has certainly impacted Gallo’s results, as he is one of the most shifted-against players in the league. However, something else is at play: luck … or lack of luck, in this case.
MLB.com researcher and reporter David Adler found this nugget of a stat to highlight Gallo’s unlucky start to the season:
“Joey Gallo had this lineout last night [April 10th] with a 112.5 mph exit velocity and a 22° launch angle. Since Statcast started tracking, there have been 132 balls hit between 112-113 mph and 21-23°. 121 of the other 131 were home runs. Gallo’s is the first one ever to be an out.”
That’s the appropriate way to view these stats. With more at-bats and games, they will carry more weight, but for now, it’s best to just enjoy them for what they are. Baseball does have 162 games in its season, and I’m sure all of these beyond abnormal stats will revert to the mean. However, it’s still fun to see luck’s profound influence just two weeks in.
Eli Blumenfeld is a first-year in the College. Rounding the Diamond appears online and in print every other week.