Twelve sensors are attached to Austin Riley’s body, from his knuckles to his heels, his head to his toes. The Braves third baseman looks more like a cyborg, something out of a Terminator movie. And actually, there are two of him, including the motion-capture image appearing on a screen over his left shoulder, in sync with his every movement.
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Riley, 25, is inside a warehouse that houses the Baseball Performance Lab at Marucci Sports headquarters in Baton Rouge, La. One baseball star after another has flocked to the lab the past two offseasons, seeking to be fitted for bats the way golfers are fitted for clubs. The players go through about three hours of testing, culminating with the exercise Riley is about to begin: A high-tech determination of which bat suits him best.
Not that Riley needs much help. He ranked fifth in the majors last season with a career-high 38 home runs. His average and maximum exit velocities were in the top 4 percent of the league. And yet, even as he barreled his way a sixth-place finish in the National League MVP voting, he could not help but notice the respective first- and third-place finishers performing at even higher levels. Paul Goldschmidt and Nolan Arenado excelled with relatively new styles of bats, featuring oversized knobs that resembled hockey pucks.
Curious about the changes, Riley spoke to the two when the Braves played the Cardinals, chatting up Goldschmidt at first base and Arenado at third. Other hitters, noting Goldschmidt was enjoying a career-best season at 34, engaged him in similar conversations, wanting to know more about the hockey-puck knob. Goldschmidt would tell them about the lab in Baton Rouge, explain the process was about more than just adding a funky new knob to your standard game model. Arenado would concur, saying, “It’s not just for the bat. It’s to see your body, the way it moves, how it can be more efficient.”
Only four years ago, the concept of bat-fitting was foreign to Major League Baseball. Players chose their preferred lengths and weights, but there was no science behind it, nothing like what was going on in golf, which embraced technological advances in club-fitting. The idea of balancing bats differently, enabling players to swing even heavier models faster, had not been extensively explored. Even now, there is no statistical evidence demonstrating the fitting process actually works, in either baseball or golf. But an increasing number of star players cite the benefits of bat-fitting.
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The transformative moment for baseball occurred during a conversation between Dr. Greg Rose, a co-founder of the Titleist Performance Institute (TPI) , and Kent Matthes, a player agent, at the 2019 PGA Show in Orlando. Matthes told Rose there was no such thing as bat-fitting in baseball. Rose summoned Liam Mucklow, a former professional golfer who had evolved into an equipment expert and TPI instructor, from the other side of the convention center.
“Can you figure it out?” Rose asked Mucklow.
Matthes connected Mucklow with Kyle Ourso, Marucci’s vice-president of sports marketing. The two went to spring training in Arizona and conducted a trial in which they paid five independent-ball players $50 each to test eight different bats. Asked to pick their favorites, the players routinely chose models that felt the most comfortable but did not, according to Rapsodo data, provide the best performance. It was an a-ha moment: Players weren’t always using the bats that could help them most.
Of course, even the perfect bat can take a hitter only so far. But Marucci, as an equipment company, naturally wants to provide the best possible bat for its clients.
On Jan. 18, 2020, Marucci announced a partnership with Baseball Performance Lab, a newly formed division of Mucklow’s original company, The Golf Lab. BPL operates out of Marucci headquarters, a complex of 12 warehouses, all painted black, on McCann Drive in Baton Rouge. Marucci once recruited potential clients by hosting them at LSU football games. With the lab, players are coming to them. Teams, too.
Eight clubs, more than one-fourth the major-league total, work with BPL. Five Silver Slugger winners in 2022 — Goldschmidt, Arenado, Nathaniel Lowe, Julio Rodríguez and Mookie Betts — worked with the lab prior to and during the season. Two other winners, Josh Bell and Luis Arráez, visited this offseason. Francisco Lindor, Joey Votto and Bryan Reynolds are among the past guests. The individual sessions cost $7,500, but for Marucci clients like Riley, the price is covered as part of his contract.
At least one former winner of a major award made the trek to Baton Rouge, but asked to remain anonymous because he endorses another equipment company. Goldschmidt and Arenado made the same request last offseason when they went to BPL with Matt Carpenter, who cited the lab as a factor in his revival with the Yankees. The two Cardinals sluggers since have signed with Marucci.
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Riley, upon getting wired up, fears he will snap one of the cords. At the behest of lab officials, he moves away from a dual force plate used for other measurements, lest the metal from the plate interfere with the electro-magnetic motion capture equipment. Each swing provides 26,000 data points, Mucklow says. The data, revealing launch angle, exit velocity and other information, processes within five seconds.
Hitting off a pitching machine can be uncomfortable with wires springing from seemingly every joint of a player’s body. Riley though, is undaunted. If Goldschmidt and Arenado did it, he can do it, too.
“Why wouldn’t you get all hooked up to see what fits best for you?” Riley asks. “I feel like the best hitters are always trying to find that little bit of an edge.”
Riley lives in Hernando, Ms., about a 5 1/2-hour drive from Baton Rouge. On the way to the Marucci lab he notices a light flashing on his dashboard, indicating he needs an oil change. Upon getting to Baton Rouge, he drops off his car at a place where it can be serviced, takes an Uber over to Marucci and walks to a nearby shop for a cup of coffee.
Not typical behavior for a player who is about to begin a 10-year, $212 million contract.
“Usually,” Ourso says, “you’re lining up black cars for guys.”
Riley arrives at the lab wanting to improve against two-seam (sinking) fastballs and four-seamers with high spin. He relays those desires to Mucklow and BPL director of player development Micah Gibbs, a former LSU catcher who played six seasons in the minors with the Chicago Cubs and Kansas City Royals before becoming an LSU coach.
Riley, mind you, wasn’t bad against either pitch last season — his .429 slugging percentage off sinkers was his lowest against any one offering, but even that was well above the .395 overall major-league slugging mark. Still, if the lab can help him identify a bat he can use, say, against a nasty sinkerballer, he’s all ears.
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For Marucci, which also manufactures its bats at the warehouse complex on McCann Drive, it’s the busiest time of year. The company makes approximately 4,000 bats for 250 to 300 players prior to spring training. A major leaguer generally uses between 40 and 60 at-bats per season, though there are exceptions. “Ozzie orders bats every day, I think,” Riley says with a chuckle, referring to Braves teammate Ozzie Albies.
The fittings are based on a metric the lab developed — Balance Point Index, or BPI. The metric, according to the lab’s website, describes the amount of energy needed to move the bat to the strike zone. It incorporates the bat’s length, weight and weight distribution into a number between 1 and 100. A 1 would be the smallest tee-ball bat on the market, Mucklow says. A 100 is based off a 35-inch, 35-ounce bat — the Nelson Cruz model.
The goal is to determine which bat a hitter moves best. There is no right or wrong answer; each player’s BPI reflects his individual characteristics, serving almost as a hitting fingerprint. Corbin Carroll, the Arizona Diamondbacks’ 5-foot-10, 165-pound outfield prospect, swings a bat with an 89 BPI. Joey Gallo, the Minnesota Twins’ 6-foot-5, 250-pound specimen, is at 77. Hitters often tell lab officials they want the Goldschmidt-Arenado hockey-puck bat. But those two bats are not the same. Goldschmidt’s has an 88 BPI, Arenado a 79.
To adjust BPI, Marucci can change the taper of a bat’s neck, the width and depth of the cup, adjust the center mass or add the hockey-puck knob as a counter-weight. The knob brings the center of mass closer to the player’s hands, making it easier to swing than a bat of the same weight that is end-loaded.
Sometimes when the lab alters a bat’s BPI, it can see a change in a hitter’s movement patterns, an adjustment in his body as he swings through the zone. Other times the movement pattern doesn’t change but the player swings at a different angle. Ourso cites Anthony Rizzo, a left-handed hitting slugger, as an example of how the process can work. The two are friends; Ourso was in Rizzo’s wedding.
Early in the lab’s development, Ourso and Mucklow recall asking Rizzo during a meeting at Wrigley Field, “What would it take to change your bat?” Rizzo replied, “Nope, not changing. Why are you even asking? That’s not happening.” Rizzo was so wedded to his model, he told Ourso, “When I put it on the scale and it weighs 31.7, it fires me up mentally.”
And now?
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“Rizzo’s got a 33-inch bat that swings like his 34 1/2-inch game bat. It’s basically relocating that barrel closer to his hands for a right-handed reliever that is going to run a cutter up under him,” Ourso says.
“It’s not like, ‘Here comes a cutter. Let me grab this bat.’ But if you see a guy running out of the bullpen, you look at the iPad and think, ‘This guy is going to try to beat me with this pitch in this spot, let me try this bat in this situation.’ From a mechanics standpoint, it’s basically choking up for him.”
As the Rizzo example shows, hitters are particular, even finicky, about their bats. At certain times in his career, Albert Pujols would request bats of both 31.8 and 32 ounces, then pick one in games based upon the kind of pitcher he was facing and whether he wanted to hit for contact or power. The difference between the two bats was so miniscule, however, some Marucci officials believed it had minimal effect.
Two years ago, Francisco Lindor, a switch hitter, asked for a .1 millimeter difference between his left-handed and right-handed bats in the thickness of the handle. Ourso thought the request extreme and told Lindor as much, but Marucci went ahead and made the bats. Ourso then challenged Lindor, asking him to close his eyes and trying to confuse him by handing him the bats in different sequences. Lindor guessed correctly every time, then signed a bat for Ourso: “I was right. .1mm. Frankie.”
Riley’s game model is 34 inches, 31 ounces. He does not want to deviate from his gamer much, if at all. But he is open to any adjustment Marucci might make within the league’s bat-density regulations, and Mucklow is eager to dive in with his latest subject.
“There’s more we could do with a baseball bat than I ever imagined,” Mucklow says.
As the lab testing begins, Riley reacts in frustration whenever any measurement of one of his body movements turn up “limited.” Gibbs, who oversees the screening, says the examination is not a pass-fail exercise. He’s simply trying to determine what Riley can and cannot do physically, detect any restrictions that might impede his swing.
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Working methodically, Gibbs measures Riley for every physical quality associated with swinging a bat. Hand size. Arm length. Wing span. Gibbs also checks mobility. Riley’s hip rotation. Shoulder rotation. Thoracic spine mobility. Pelvic control. And more.
After the measurements, Riley moves on to the “horsepower test”: a vertical jump to measure lower-body strength; an overhead toss of a medicine ball at the end of a sit-up to measure core strength; and a chest pass of the ball to measure upper-body strength.
As Riley finishes his chest pass, Mucklow starts tapping on his calculator and inputting the third baseman’s results, all of which were above average for a professional player. The calculator displays a number: 119.95. Mucklow, working off a formula the lab created, declares it Riley’s potential maximum exit velocity.
Only one major leaguer had a higher exit velocity than 119.95 last season: Oneil Cruz, who registered 122.4. Riley’s maximum of 115.9 ranked 16th in the majors. So how does Mucklow come up with 119.95? He explains that because Riley seeks contact during games, he is not swinging at maximum speed. But if Riley tried to max out against a pitching machine delivering balls down the middle, he could squeeze out the few extra mph necessary to reach 119.95.
Mucklow and Gibbs, however, are not simply trying to measure Riley’s physical capabilities. They also want to get a sense of Riley’s “feel” for a bat’s properties, and conduct two experiments to gain that understanding.
In the first experiment, Riley closes his eyes and is given two bats to hold, one at a time. Mucklow asks which bat is longer. Riley picks the shorter bat, then opens his eyes, saying, “damn,” upon learning he picked the wrong one. Eighty percent of major leaguers make the same choice, selecting a 33-inch bat with an 85 BPI over a 34-inch model with a 78. The shorter bat is end-loaded, making it seem longer.
In the second experiment, Riley grabs his game bat, holds it upright and closes his eyes again. Mucklow directs him to take his top hand off the bat and grab the sweet spot with two fingers before it drops to the ground. Kiké Hernández missed the bat entirely when he went through the exercise. Riley does not, but when told of Hernández’s result, he says, “I was honestly worried I was going to do that.”
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Not that Riley should have been embarrassed: The experiment is simply designed to demonstrate how a player’s sweet-spot awareness might change as he tries bats with higher and lower BPIs. Mucklow says some of the lab’s best results have come after relocating the sweet spot so it’s more in line with what the player feels.
His preliminary testing complete, Riley moves to the batting cage. Lab officials advise visiting hitters to follow their normal routines, so Riley begins by taking flips from Gibbs, standing on a dual force plate. Outside the cage, lab technician Jameson Fisher, a former White Sox farmhand, sits at a desk and stares into a computer monitor, viewing data. On one screen above them, a six-camera system shows Riley from various angles. A second, larger screen displays a series of graphs, measurements of how various parts of Riley’s body — as well as his bat — are moving. The measurements, in essence, form the DNA of Riley’s swing, providing future reference points if he experiences an injury or slump.
During a break, Riley mentions that he wraps the knob of his game bat with a thin piece of athletic tape, just to provide extra support. Ourso tells him Marucci can cut a bat to achieve the same effect, and departs for another warehouse on the site where bats are manufactured. Within the hour, Ourso returns, new model in hand. Riley grips it and immediately gives his approval, saying, “Now I won’t have to put tape on it.”
For the final phase of testing, Riley gets wired for motion-capture analysis, with Gibbs, Mucklow and Fisher placing and adjusting sensors on his body. The process takes several minutes. From a distance, Riley catches a glimpse of his motion-capture image. “Seeing your body up there, the robotic movements, it’s pretty cool,” he says.
Riley warms up with his game bat, which has an 81 BPI. He then tests six bats — three puck and three non-puck — with BPIs between 80 and 88. Fisher feeds balls into a pitching machine. Gibbs monitors the data. One of the screens displays Riley’s motion-capture image. The other shows his exit velocity, launch angle, spray direction and “player rating.” To establish that rating, Riley shouts out a number, between 1 and 10, after each swing. The subjective evaluation acknowledges the importance of his own feel, and comprises about 15 percent of the overall assessment.
As Riley switches bats, lab officials check for changes in his movement patterns, the tiniest of details that might provide the difference between a barrel and a swing-and-miss. Mucklow notices cleaner movements when Riley uses puck bats with the center of mass closer to his hands. One such bat is two ounces heavier than his gamer, but easier for him to swing. His wrists stabilize, get into a more neutral, powerful position.
At the end of the session, Riley pulls up a stool in front of the screens to review his data. Mucklow explains a hitter creates force in three ways — horizontally, by moving toward and away from the pitcher; vertically, by pushing his heel down into the ground; and torque, by spinning his torso. He is particularly complimentary of Riley’s heel strike, noting the player does not drift the way hitters sometimes do when overwhelmed by velocity. Riley responds that he struggled with that issue throughout his time in the minor leagues, and finally corrected about two years ago.
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“Honestly, I can go through a whole bunch of cool detailed stuff on biomechanics that I love looking at. But a lot of the stuff you do, whatever your hitting guy has you working on, stay the course,” Mucklow says.
“That’s the plan,” Riley says.
Riley, though, did not depart without a new toy. The company will add a fresh model to his bat shipment for spring training. The bat will be a 1/2 inch longer and 1.1 ounces heavier than his gamer. It also will feature a hockey-puck knob and a slightly higher BPI — 82, as opposed to 81.
The new recipe, Mucklow says, is designed to help Riley better handle sinkers and better cover the inside part of the zone. While using the bat during his motion-capture session, Riley impressed Gibbs by pulling an inside pitch fair. Riley said he normally would have hit the ball foul, into the third-base dugout. Counter-intuitive as it might sound, the longer bat gave him better inside coverage. And while the bat was heavier, it was also more balanced. Thus, Riley could move it with more control.
Hitters seem to relish the lab’s process, which provides new insight into their craft. Yet for all the lab’s work on bat-fitting, all the transfer of information from the golf to the baseball worlds, Mucklow says, “There is still no study that has ever proven that golf-club fitting lowers handicaps.” Which leads to an obvious question: Where is the proof bat-fitting actually works?
The offensive WARs of the lab’s clients provide one indication, though Mucklow acknowledges a variety of factors sway that metric. Assessing every at-bat of the players who get fitted and every bat they use would be too massive an assignment for the lab’s analytics department.
But two of the teams under contract to the lab do precisely that work, and Mucklow says both have proposed contract extensions.
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A player’s mindset also factors into the equation.
“We believe if someone goes through our process, even if we recommend they stay with the same bat, they’re going to take that bat into the game with a higher level of confidence — and higher confidence breeds better performance,” Mucklow says.
Bat-fitting also is only part of the lab’s mission. From a top-down camera, lab officials recently noticed an accomplished major-league hitter not getting enough internal hip rotation. The lack of rotation caused his front foot to spin out, which in turn caused him to lose force prior to contact. The player, who did not want his identity revealed because his issue stemmed from an old injury, can now take measures to address the problem.
A diagnosis of a different sort occurred last August, when the Mets’ Brandon Nimmo was debating whether to use a leg kick or toe tap. With the leg kick, the lab’s testing showed he lost stability in his pelvis, and his heel strike suffered. As Nimmo puts it, “I had a better kinetic sequence when I did the toe tap, and therefore could be more consistent and put more into the ball on a more consistent basis.”
Before the season started, the lab also helped Nimmo identify the bats that work best for his swing. “You are no longer guessing at what you are feeling,” Nimmo says. “There are actual numbers to support what you are feeling now.”
Goldschmidt, when he visited the lab with Arenado and Carpenter last offseason, was not looking to make a change, particularly after his game model tested well. The lab, however, suggested a few slight modifications, including the hockey-puck knob. The adjustments, in Goldschmidt’s view, made a difference. “I felt it when I was hitting,” he says.
Players can’t be fooled. Players always know. Which is why Riley was willing to drive 5 1/2 hours to Baton Rouge on the first day of February, then allow the lab to transform him into a cyborg. The Contreras brothers, Willson and William, visited the lab two days later, along with the Cardinals’ Juan Yepez. Arráez was in on Monday, David Peralta on Tuesday. Alex Bregman is up Friday.
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“I have my main model, my go-to, it hasn’t treated me wrong yet,” Riley says. “But if you face a guy who may have your number because he’s got a certain pitch that is tough to get to, if I can move the center weight a little closer to me with a different bat, get a little bit more launch angle, the next thing you know you hit a single, a double …”
And there it is. The difference Riley is seeking. That extra edge.
(Top image: Eamonn Dalton / The Athletic; Photos: Casey Sykes / Getty Images; courtesy of Marucci)
