Furi Sport, a new tennis equipment and fashion line, wants to do nothing less than change the game.The first time Erick Mathelier visited Greenwich, Conn., was an eye-opening experience.“The houses were humongous,” he recalled, sitting outside a Lower East Side cafe one morning in June. “I was like, ‘Wow, people live like this?’” To the eyes of a teenager from the East Flatbush neighborhood of Brooklyn, Greenwich was a window to a different world, one where the houses weren’t just bigger, the dreams were.His first glimpse of this rarefied enclave on the Long Island Sound came through tennis, in a van on the way to an Ivan Lendl tennis club for a match.Tennis was a gateway for Mr. Mathelier. He recalled his first time on an airplane at age 14 for a trip to a tournament in Bermuda. “It’s funny, I was teased because I was so scared to fly, and by 14 most of my friends had flown,” he said. The sport was his ticket to a scholarship to a Division 1 college, Saint Francis in Brooklyn Heights. Two decades later, Mr. Mathelier, now 42, is a tennis professional — off the court.Last month, he introduced Furi Sport, an equipment — rackets, strings, overgrips and bags — and apparel line with his business partner Michelle Spiro. The idea behind the company is to break down the entry barrier to tennis, to shake off the elitist country-club flavor that insulates the world of Wimbledon and its all-white dress code.Black is the defining color of the Furi Sport T-shirts, hoodies, bags and rackets. At $199, the rackets are priced with inclusivity in mind, competitive with, yet slightly below, the top of the competition (Prince, Head, Wilson, Yonex, Babolat). Mr. Mathelier knows from experience that tennis can take you places, if you can gain access to it.How Others LiveMr. Mathelier grew up in a predominantly Caribbean neighborhood in Brooklyn, the only son of a single mother from Haiti. He was an active child whose first love was baseball. As a 10-year-old, he was one of two African American kids on a team in Sheepshead Bay.Then, in the summer of 1989, Yusef Hawkins, a Black teenager from East New York, was brutally murdered by a mob of white kids in Bensonhurst. As racial tension surged in the city, Mr. Mathelier’s mother pulled him out of baseball, fearful that Yusef Hawkins’s tragic fate would befall her son.“I was so sad,” Mr. Mathelier said. “I needed something to do.” Deeming himself too short for basketball, he set his sights on tennis. Why? He’s not sure. His mother told him to crack open the Yellow Pages and find a way to play, which led him to the Prospect Park Tennis Center.The tennis club, situated at the nexus of the neighborhoods of Park Slope, Little Caribbean and Crown Heights — which at the time was years away from being gentrified — drew a diverse bunch.“Just seeing how people lived definitely changed my perspective,” Mr. Mathelier said.Mr. Mathelier had no professional tennis ambitions until he met Ms. Spiro by chance at a fashion event in 2014. By then, he had hung up his racket to focus on a series of start-ups.Ms. Spiro, 53, spent 25 years in corporate fashion in increasingly senior buying and sales roles at Macy’s, DKNY, Polo Ralph Lauren Underwear and Calvin Klein Men’s Underwear — companies that were held by public giants like Sara Lee and Warnaco. By 2015, she had become intrigued by the street wear movement.“The luxury market was all about showing how much money you have through what you were buying,” Ms. Spiro said. “What I loved about street wear is that it was this exclusive inclusivity. The currency changed from cash to being in the know.”Mr. Mathelier’s teenage tennis journey resonated with Ms. Spiro, who observed that Supreme, Palace and A Bathing Ape were anchored in skateboarding. Moncler and The North Face grew out of outdoor recreation, and Carhartt and Timberland were backed by construction. Tennis had no street cred.Ms. Spiro called Mr. Mathelier and said, “I have this crazy idea.” How about a rare Black- and female-owned tennis brand, based in New York City and built on the idea of taking the sport out of the country club?The company’s clothing collection speaks to tennis’s off-court culture.via FURI SportThe vibe is more streetwear than country club.via FURI SportTennis for EveryoneHigh-quality, competitive equipment was central to the idea. But there’s a reason the sport is dominated by a handful of big brands. “Everyone is just stuck with what equipment that they’re used to,” said Mr. Mathelier, who was committed to Prince before founding Furi. “Even though they may complain about the newer version of their racket, they just play with it.”Then there’s the fact that what looks like a relatively simple piece of equipment requires navigating a byzantine network of Asian manufacturing cliques. Ms. Spiro and Mr. Mathelier enlisted his childhood friend from Prospect Park Tennis Center, Gerald Sarmiento, a pro-shop owner, coach and master stringer who knows the nuances of rackets better than his own backhand. He told them not to bother unless they came to the market with something that gives the player an “ooh-ahh feeling,” Mr. Mathelier recalled.When it came time to develop a racket, Mr. Sarmiento connected them with Yasu Sakamoto, a Japanese racket maestro with 40 years of experience consulting for companies including Wilson.Through several years of development, frustrating trials and errors, they landed on a proprietary design with energy return technology and vibration reduction technology that gave Mr. Sarmiento that special feeling. Two models, a lite and a pro version, are for sale on the Furi Sport website.The next challenge was recruiting other players. “People would be like, ‘Oh, that’s cute,’” Mr. Mathelier said of pitching Furi’s racket. Once, at the McCarren Park courts in Brooklyn, he approached a friend and her hitting partner.“He looked at me like I was a traveling salesperson with my trunk,” Mr. Mathelier said. “Well, now he plays with Furi.”For every dismissal, there was someone willing to help. A tweet sent to Caitlin Thompson, the publisher of the independent tennis magazine Racquet, led to a meeting. “We became hitting partners because I was really intrigued about the idea of new equipment in the space,” said Ms. Thompson, who has used the Furi rackets, grips and bags.She sees Furi’s opportunity in its positioning as a beginner-friendly option for recreational players, a rare direct-to-consumer brand (think of what Casper did for mattresses) in a market steeped in pro-shop culture.“So much of tennis is catered toward this notion of professional athletes,” Ms. Thompson said. “This is a racket that Roger Federer plays with. This is the racket that Serena Williams plays with.” She said that Mr. Federer’s racket is so heavy, most recreational players can’t lift it above their heads. Yet pro shops can’t keep it in stock because he plays with it.The Social ComponentFor Mr. Mathelier, Furi is a tool to reach kids growing up in circumstances similar to his own. Junior rackets will be coming for fall. Furi is sponsoring three junior tennis players — Carter Smallwood, Olivia Medrano and Bode Vujnovich — and donates grips, strings and rackets to youth programs, including Kings County Tennis League, which began in 2010, when its founder Michael McCasland posted a sign offering free tennis lessons on a dilapidated court near the Marcy Houses in Bedford-Stuyvesant. It has since grown into a tennis program for kids living in Brooklyn public housing that serves more than 200 people.“You can use tennis to get out,” Mr. Mathelier said. “It is really good at creating structure, building strategy. A lot of former tennis players end up becoming successful businesspeople.”The lifestyle portion of Furi Sport draws on Ms. Spiro’s expertise. Luis Santos, a designer who has worked for Christian Lacroix, Kenzo and Paco Rabanne, created a collection of clothing that is not performance wear — that’s still in development — but speaks to tennis’s broader, off-court culture. T-shirt dresses, shirts with cutout shoulders and wide-leg, tapered khakis and cargo pants can be worn by anyone heading to a post-match drink. Or anyone who wants to be in Furi’s club.A blue tennis ball with a smirk is Furi Sport’s trademark, “symbolizing the fierce energy and velocity that comes from within,” according to the company’s website. The name Furi was chosen partly because “fury” evokes an attitude of fire-in-the-belly grit essential to a sport in which every match results in one winner and one loser.“You have to be comfortable with losing,” Mr. Mathelier said. “We have a saying internally,” Mr. Mathelier said. “‘Dream big and let it fly.’” He directed attention to his forearm, where those words have been immortalized in a subtle, faded tattoo. More