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Miami’s new synthetic turf creating a home-field advantage for Marlins?

Ground balls at LoanDepot Park have been yielding unusual results depending on who hits them.

A detailed view of the new B1K: Batting A Thousand by Shaw Sports Turf synthetic turf during an intrasquad simulated game at Marlins Park Photo by Mark Brown/Getty Images

Two years ago, the Marlins removed the natural grass at their home ballpark and installed a synthetic surface. They downplayed the product’s potential impact on gameplay, touting the qualities that allowed it to “closely mimic” the old-fashioned stuff. Nonetheless, I was anxious to see the B1K baseball system in action.

Understandably, the surface change receded to the back of our minds once the COVID pandemic derailed Major League Baseball in early 2020. The Marlins were supposed to host their first game on turf on March 26. Then, that date became July 27 on the revised, short-season MLB schedule. In the aftermath of the team’s infamous COVID outbreak, the home opener was pushed back further to August 14. By then, nobody cared about the damn grass. Even if they did, the lack of traditional media access and fan attendance during the turf transition year has prevented this story from being adequately told.

Since 2020, the Marlins have performed decently at what is now known as LoanDepot Park. They’re just a tick below the .500 mark at 53-54. On the road, they’ve had a lousy .391 winning percentage (45-70 record). Their run production at home is nearly as high as it is elsewhere despite the venue’s reputation for suppressing offense, while their pitching and defensive splits are too extreme to be attributed to environmental factors alone.

Miami’s synthetic turf is helping the home team, and I’ve got Statcast data to back that up (courtesy of Baseball Savant).

Bryan De La Cruz singles on a ground ball up the middle

Since Marlins Park/LDP was erected a decade ago, the Marlins have led all of Major League Baseball in ground ball rate. By a wide margin, too—the gap between MIA (48.2 GB%) and second-place SDP (46.0 GB%) is larger than the gap between SDP and 16th-place STL (44.1 GB%). That’s not a good thing. More than three-quarters of grounders at the major league level are converted into outs. Even the well-struck ones seldom yield extra-base hits and never yield home runs.

I am going to narrow our focus a bit since Statcast hasn’t been around for that entire period. From 2016-2019, ground balls at LoanDepot Park—Marlins and their opponents combined—produced a .247 batting average. From 2020 to the present, that figure has been .246. Practically identical, right?

But try to process this:

  • .280 ground ball batting average (340-for-1,213) for Marlins batters at home since turf was installed
  • .216 ground ball batting average allowed (275-for-1,274) by Marlins pitchers at home since turf was installed

That disparity has been deciding games in the Fish’s favor.

Offensively, the turf-tastic Marlins are faring better on grounders than any other MLB team is at home, 12 points up on the Angels (.268). Their average exit velocity on these types of batted balls, 84.6 miles per hour, is similar to the league’s overall 84.3 mark. They are overachieving their .248 expected batting average by 32 points. However, expected weight on-base average (xwOBA) takes the extra step of accounting for batter Sprint Speed—the Marlins’ grounders rank tied for fifth in that category.

Individual Marlins who have had particularly high home ground ball batting averages since 2020 include Bryan De La Cruz (.404), Garrett Cooper (.364), Starling Marte (.333), Miguel Rojas (.324) and Lewis Brinson (.314). What do they all have in common? Right-handed batters. They face fewer infield shifts than their lefty counterparts, and even when fielders get a glove on the ball, they must make longer throws to first base to record the out.

Although the Marlins overall offense has been bad so far in the turf era, their roster’s fast, right-handed-heavy composition has boosted their efficiency on grounders.

Ground ball spray chart for Marlins batters in home games since 2020
Ground ball spray chart for Marlins batters in home games since 2020
Baseball Savant

Batted ball direction on grounders is a key difference between the Marlins’ success and their opponents’ frustration, as visualized below. With the exception of Trevor Rogers, Miami’s pitching staff has been relying on righties since 2020, leading visiting teams to counter with a disproportionate numbers of lefty bats, making life easier on the infield defense.

Spray chart of ground balls allowed by Marlins pitchers in home games since 2020
Spray chart of ground balls allowed by Marlins pitchers in home games since 2020
Baseball Savant

It also seems as if Marlins pitchers are skilled at inducing weak contact. Their .215 xwOBA allowed on home grounders is the best in baseball. They’re tied for fifth-best in average exit velo at 83.5 mph.

I was curious whether Marlins infielders (under the direction of Trey Hillman) had been positioning themselves differently at LDP vs. elsewhere, making adjustments that they felt could be advantageous on turf. Statcast says this was not the case, but I did stumble upon one fun fact: Marlins infielders since 2020 have set up closer to home plate than any other team. The combined starting distance from home for their first baseman, second baseman, third baseman and shortstop averaged 520 feet (MLB average was 529 feet).

Let’s see whether Al Pedrique, Hillman’s successor on the coaching staff, continues with that approach.

At first glance, the B1K system is doing its job at mimicking natural grass. It has treated the Marlins well thus far, but that appears to be almost entirely a reflection of their personnel, and the good fortune hasn’t been enough to offset their power deficit.

Completing their 2021-22 offseason with a trade for Orioles star center fielder Cedric Mullins would give the Marlins the best of both worlds—he is a ground ball savant who also launched 30 home runs during his breakout year. If Mullins isn’t attainable, they are expected to fill out their lineup with the acquisition of a more conventional veteran slugger. Their mighty grounder batting average could suffer as a result, but that trade-off would be well worth it.