It’s common knowledge that ground balls are far from productive batted balls. Pitchers strive to balloon their ground ball rate, reducing risky fly balls and line drives. Pitchers can often supplement low strikeout rates with high ground ball rates. Batters crave launch angle and sky-scraping fly balls. There’s a sport-wide stigma around ground balls. Major League hitters just aren’t as productive once they drive the ball into the ground. While this stigma is backed by data, it’s not completely cut and dry. What you envision when you hear ‘fly ball’, generally a flyout, may not be quite as valuable as it’s made out to be.
In 2019, Major League Baseball collectively batted .236 on ground balls, with a .258 slugging percentage (.022 isolated slugging). In contrast, fly balls resulted in a hit 25.4% of the time, with a hefty slugging percentage of .758. That’s an impressive slugging percentage, especially considering it’s league-wide, emphasizing just how valuable fly balls can be. This simple detail is what has inspired hitters to elevate their launch angles. When each at-bat results in an additional half a base, who wouldn’t want to put the ball in the air?
|MLB (2019)||Batting Average||Slugging Percentage|
But a quick eye will spot the stark contrast between the ordinary batting average and mammoth slugging percentage. The average additional number of bases acquired when graduating from ground ball to fly ball increases much more rapidly than the number of hits. The contrast between BA and SLG on fly balls is so great that it obsolesces ISO (.535). Even considering the significantly larger ground traditionally covered by fewer fielders, fly balls are exponentially more “productive” while producing only a few more hits. Except, it’s not really fly balls contributing to the robust extra-base value of balls put in the air.
Instead, it’s home runs. There’s some ambiguity here. A home run is generally a fly ball, but never a ball in play. It counts toward fly ball percentage, but not BABIP. Nobody’s calling that into question. But it does mean that the value of fly balls and ground balls must be handled with care.
Considering ground balls don’t have this handicap (A player’s BABIP and BA on ground balls will always be the same) the value of ground balls and fly balls, from a certain point of view, can be considered skewed. It’s not a solid argument. Hitting more fly balls does increase your chances of hitting a homer, and home run often implies fly ball. But because fly ball far from implies home run, let’s consider the value of fly balls without dingers. Removing home runs from the equation changes the ground ball/fly ball calculus quite a bit. From a balls in play – no home runs – perspective, ground balls are much more valuable than fly balls:
|2000 through 2019:||BABIP|
In 2019, ground balls were twice as likely to become a hit than non-home runs fly balls. That’s a massive difference. This is insightful and fascinating, but it doesn’t offer much value in the scope of Major League Baseball as a whole. That’s because nearly all hitters are capable of hitting enough home runs to offset the number of fly balls that land in an outfielder’s mitt. It’s similar to how strikeouts are tolerable for batters who club home runs at a high rate.
There was one batter, however, who, despite the odds would have been more productive hitting additional ground balls: Tim Locastro. Granted, it’s such a minor difference, it’s likely noise. However, theoretically, if Tim Locastro hit all of his 170 batted balls in 2019 on the ground or any more than the 78 he did, he would have had an improved 2019 season.
|wOBACON (2019 Season)||wOBA (2019 Ground Balls)||Difference:|
This is a unique, serendipitous amalgamation of factors, not just home run rate. Most notably, Locastro also failed to produce an effective wOBA on all batted balls, his wOBA on contact was 28th worst of all 320 hitters who had at least 250 plate appearances in 2019. This made it easy for him to beat that number on just ground balls. Tim’s 0.4% home run rate, had he qualified, would have tied him with Yolmer Sanchez for the worst in the major leagues. Without any home runs fortifying the value of his fly balls, Locastro ran a .113 wOBA on fly balls (second-worst in the league) versus .321 on grounders. Ultimately, that wOBA on ground balls overcame his wOBA on all contact (.312), including home runs and fly balls.
Does all this mean Locastro should focus on hitting ground balls all the time? Not yet. He’s better off increasing his launch angle (12.3) and boosting his exit velocity (83.5) to hit more home runs, extracting more value out of the fly balls he does hit. But it’s a fun thought experiment.
|Tim Locastro (2019)||Jeff Mathis (2019)|
|wOBA on Ground Balls||.321||.221|
|wOBA on Fly Balls||.113||.094|
I mentioned Tim Locastro had the second-worst wOBA on fly balls in the league in 2019. Beating him out for the top spot was Jeff Mathis with a .094 wOBA. While it may seem Mathis could also benefit from hitting more ground balls, that’s not the case. Mathis has less distance between his wOBA on fly balls and that of his grounders’. His wOBA on ground balls was 2.35 times that of his fly ball wOBA compared to Locastro’s rate of 2.84. Thus, Locastro’s opportunity cost of surrendering fly balls was lower allowing him to climb into a more prosperous position much faster.
Especially with batters hitting fly balls engineered to sail beyond the outfield fence it’s likely there will never be a legitimate scenario where a player should be swelling their ground ball rate (though perhaps there would have been in the past). Player development works against it, as it should. But next time you hear about fly balls being more valuable than ground balls, make sure those fly balls include home runs!
All data was sourced from baseball-reference.com, fangraphs.com and baseballsavant.mlb.com.