Former Mariners Minor League strength and conditioning coach Michael Sadler remembers his first time meeting Cal Raleigh in 2019, out in Single-A Modesto.
"He'll probably kill me for saying this, but it looked like he had a lot of baby fat on him," Sadler laughed. "Kind of a baby face. Big body, but not really toned out at all."
Still, Raleigh had the unique makings of a future big leaguer. He was 6-foot-2 and more than 200 pounds. He could hit, with power, from both sides of the plate. He proved he could handle his own on defense that year -- putting up a caught-stealing percentage that was above the California League average.
And there was one other thing he had from the start that Sadler remembers. A fairly, well, rotund thing.
Something that would help him, and has helped many others, during their meteoric rises to the big leagues. It would help him catch nine innings for 162-game seasons. It would help him hit 60 home runs. It would end up defining him in many ways -- written on T-shirts and signs, etched on the bottoms of bats and portrayed in Porta-Potty ads.
"People didn't call him The Big Dumper yet," Sadler said. "But it was like, 'Oh shoot, that guy's got a huge [butt].'"
---
Bigger backsides have likely always been a thing for baseball players.
Look at early 20th-century star Honus Wagner, still showing it off at 59 years old. You may know Lou Gehrig as the Iron Horse, but he also had another seldom-used nickname: Biscuit Pants. Stan Musial knew how important those core muscles were to hitting .300 year after year.
As four-time Manager of the Year Buck Showalter once said, "You don’t see a lot of good power hitters or good pitchers that generate arm speed that don’t have a good, high butt on them."
Tighter uniforms, better nutrition and more intense workouts have brought modern-day big leaguers into an entirely different rear-end realm. There are blogs ranking the biggest, the fittest, the best.
But why has it always been such a thing in baseball? Why is it so important?
"I'm so glad you asked me, because this is such a fascinating topic," Bret "The Glute Guy" Contreras told me in a call. "I've been thinking about this for years."
Contreras is one of the leading experts on the glute muscle you can find.
He owns three gyms across the country called Glute Labs. He has more than 1.5 million followers on Instagram under the username "The Glute Guy." He has his PhD, CSCS (Certified Strength and Conditioning Specialist) in Sports Science -- concentrating on that crucially important lower half of the human body.
"I did my thesis on the glutes," Contreras laughed.
Contreras says baseball players having big glutes could be both genetic and due to robust resistance training techniques. Taking one look at Raleigh, he thinks he had some help on the genetic end (Sadler confirmed this, saying "he can thank his mom and dad for that.")
Either way, having strong, large glute muscles is absolutely a benefit on the diamond.
"In baseball, it's very anaerobic, very power-oriented," Contreras told me. "It's not an endurance sport. You explode for a few seconds and then you're done. When you're sprinting to first base, that's using your glutes. When you're swinging a bat, that's using your glutes. I remember Don Mattingly back in the day, he was my favorite. He would get way back and load up on the back leg. When he swings, he's actually doing all three actions of the glutes at once: You're doing hip extension, hip external rotation and hip abduction at the same time."
"It's about using the ground to create force," Sadler chimed in. "In Cal's case, you have a big lower body and he's got a great swing. If he connects on a ball, it's going 400-plus feet because he uses that lower half so well. It's just synched up throughout his swing."
Raleigh also has the benefit that he's a catcher -- squatting for around two hours every game. That develops his lower half more than any other position.
"It's like an isometric hold for the glutes," Contreras said.
As you've probably seen, or maybe heard in a classic 1990s baseball movie, some of the most powerful pitchers also tend to have a bigger behind. It helps them out the same way it helps a batter.
"Yeah, all three of those actions are carried out when you're pitching as well," Contreras explained. "Those rotational sports, you're using the glutes. They say the glutes are a triplanar muscle because they work in all three planes."
It's such a crucial muscle, you'd think scouts would be on the lookout when grading younger prospects. And that's true, many of them are.
"Let's talk about butts," Twins VP of International Scouting & Special Advisor to Baseball Ops Kevin Goldstein told me in a call.
Goldstein has worked in MLB scouting departments for years -- 10 seasons with the Astros and now entering his third year with the Twins. Although he hasn't heard of a team having "a box on their scoring sheet where they grade the guy's butt," it is an area of the body scouts take a mental note on. It can determine how much power and growth they'll have over the next couple decades. Ken Griffey Jr.'s report from the 1980s famously had a note about his "thighs and buttocks" -- something not uncommon in a prospect's notes section.
"Power is generated by the core, right?" Goldstein said. "A big part of your core is your butt. Think about guys with a ton of power. Obviously, Raleigh just hit 60. Kyle Schwarber, Aaron Judge, [Eugenio] Suárez. Even young guys like [Junior] Caminero. These guys have big cores."
But it's not exactly an end all be all for success in the big leagues. A slimmer star like Byron Buxton is a five-tool player who hit 35 homers last year. The incredibly slender Chris Sale is likely a future Hall of Famer.
"There's kind of two ways to generate power," Goldstein told me. "There's strength with core stuff and then there's twitch power. Nothing in baseball is universal. We can always pick out weird exceptions and all that stuff, guys who don't do it the normal way. That's one of the beautiful things about the game. We nonetheless bet on what tends to work"
"And big butts tend to work when it comes to power."
Speaking of players with big butts ...
"There's no easy way to get into this, is there?" Anthony Recker laughed. "Just dive right in."
Former big league catcher and current MLB Network analyst Anthony Recker was known for a few things during his career. His solid defense, his ability to hit some clutch home runs and, well, how can we put this: His larger-than-life behind.
It may be one of the most talked about in recent baseball history -- there are websites, Facebook groups, Instagram pages, X and even Tumblr carousels dedicated to it.
"I had nicknames as a kid, it just comes with the territory," Recker said. "A hereditary gene more than anything else. I don't even wanna know what my nicknames were. When I was a kid, when I was 10 years old, teammates were calling me bubble butt."
Recker, of course, keeps all of his muscles in pretty good shape throughout his body. You can’t just have strong glutes and nothing else. It’s all about making sure everything flows together for baseball success.
“If you are strong in your glutes, you have to connect it all,” Recker told me. “Your core, your back – up through the spine. Into the shoulders. Everything. Down into your hamstrings, which connect to your glutes. All of that helps you from a power perspective and power output.”
Like Sadler, Recker reiterates that the ground is where most hitters get their force. Pushing off that with a big lower half is essential to success at the plate.
Still, as much as Recker would like to point out other areas of his body or maybe talk about his dingers or that time he pitched a 1-2-3 inning as a position player, he seems to understand that his behind is front-and-center. Behind-and-center? Even other former players he never played with know him for it.
"I was working on MLB Network one morning, the first time I met Cliff Floyd," Recker said. "And he's like, 'I know you!' And he starts telling me about all these websites and stuff. I'm like, 'OK, whatever.' You know, it's out there. It's seen. People find it. It is what it is."
---
Back in Modesto, even though a broad backside was a known feature of Raleigh's, it wasn't really talked about publicly.
Raleigh wasn't even really into the Big Dumper nickname when teammate Jarred Kelenic first bestowed it upon him in the Minor Leagues around 2020. But his trainer, Sadler -- who's now one of his best friends -- says Raleigh definitely worked on building up his gluteal region during their time together.
"He loved to do barbell glute bridges and hip thrusts," Sadler said. "I tell you what, he'd put five plates on each side and just rep 'em out. He'd rep out like eight to 10. And I'd be struggling to just get, like, one of them."
But since it's caught on in the Majors, Raleigh has slowly embraced the moniker.
“It’s Dumper, Dumpy, Big Dumps,” he told GQ last summer. “Everyone’s got their own little version. It’s what I am now."
And just as the legend of the nickname has grown in popularity over the last six years, so has, according to Sadler, the dumper itself.
"I'd say it's increased in size a little bit, yeah," he said, laughing.
Raleigh was interviewed last summer saying his broad bottom half was "a gift and a curse," but Contreras -- a man who's published scientific papers on the glutes, the dumper, the derrière; however you might refer to it -- believes there's no more essential muscle to an athlete's success.
"Look at a muscular anatomy chart, what stands out? What's the keystone? What's the piece that ties the upper and lower body together?" Contreras told me. "It's the centerpiece. It's like a Swiss Army Knife."
And no, as seen with Raleigh, Recker, Griffey Jr., or many of the thousands of players who've used it it reach the highest level of the sport, it can never be big enough.
"It's never a detriment," Contreras said. "The bigger the glutes, the more the power."