



Earlier this month in this tiny, mountainous country—while most of the world's top players were preparing on hard courts for the U.S. Open, which begins Aug. 26—Barnett faced 40-year-old Italian Enrico Becuzzi on clay in the first qualifying round of the San Marino Open, a stop on the ATP's Challenger Tour. This is the other pro tennis circuit, and it is distant in every way from the world's best players who will gather for the U.S. Open.

Here in San Marino and at other Challengers around the world, low-level players, some harboring Grand Slam dreams, hone their games and try to bolster their rankings. Journeymen such as Barnett and Becuzzi compete before generally sparse crowds for cash prizes that often don't cover travel and other expenses. Almost every elite player has stopped at this level, briefly, before graduating to the big leagues. Many other players, though, remain at this level and eke out a living.

So far, Barnett isn't in either of those groups. After Becuzzi beat him 6-1, 6-2—Becuzzi's third win in his last 71 singles matches—Barnett fell to 1-13 in pro singles since 2010. He doesn't currently have a singles ranking. He's done better in doubles (ranking: 1,223rd), winning two matches in 21 tournaments and all of his career prize money—his share of less than $9,000, before taxes.

Sam Barnett lost to Enrico Becuzzi in the first qualifying round of the San Marino Open. Carl Bialik

Barnett and his doubles partner, the American veteran Kevin Kim, made €460 here (about $614) for losing their opening match to an Italian pair, winning just three games. Barnett served well but returned poorly. "He play a little bad," said one of his opponents, Marco Cecchinato, who hadn't heard of Barnett before the match.

But Barnett's view of his pro career is more positive than the returns. "Everyone appreciates hard work and everyone appreciates ambition," he said. "Even in the matches I've lost, every time I'm on the court, I'm earning a little bit more respect."

And he has already achieved his main goal. Growing up in Chicago, he asked his coach, Mike Benson, if someday he could attain a world ranking. Benson said yes, given enough time. Barnett earned a ranking in doubles last year by winning his first match, then reached a peak of 801st last month with his second win. Eventually he'd like to reach an event on the top circuit, the ATP World Tour.

Barnett also soaks up the atmosphere at events such as the San Marino Open, with its picturesque setting in the cradle of the world's self-proclaimed oldest republic. The tournament once was a major tour event. These days it and other Challengers are struggling to make ends meet, especially in Europe, where sponsors are struggling economically. Fans still pack center court for marquee matches, such as nighttime meetings between two Italians. For the more serious tennis fan, the undercards offer something the major events cannot: courtside seats, chats with players after the match, sometimes even a meal next to them at the tennis club's restaurant. (Also, the chance to attempt to pay to fix matches, a problem players say is common with prize money so low at these events.)

Many fans follow players such as Barnett and Becuzzi closely. There's admiration for their perseverance despite rarely winning—not to mention a certain allure in the idea that some pros' level of play is not much higher than their own. "Becuzzi versus Barnett for a tennis fan is like the Champions League final for a soccer fan," tweeted Stefano Berlincioni, who describes himself as a chemical engineer in Italy. "I would pay an expensive ticket to be there."

At a tournament last summer in Bogota, boys asked Barnett to sign their Frisbees. "I don't know how many other mathematicians in the world have ever been asked for their autographs," he said.

Despite Barnett's struggles on the court, Benson, his coach, said he always had the potential to be a solid pro. When he was 11, Barnett was diagnosed with Crohn's disease, a gastrointestinal disorder that can be debilitating. Benson said he helped Barnett model his game on Jimmy Connors's, to "stand on the baseline and rip them," he said, "because he didn't have the stamina to play long points for years and years."

Doubles, with a partner to share the court, helps. So does the fact that Barnett's biggest strengths—his returns, serve and volleys—are the most important skills in doubles.

But his movement, consistency and handling of high bounces could all use improvement.

Was it worth crossing the Atlantic for 100 minutes of match play? "You gotta try," he said.

When he was an undergraduate at the California Institute of Technology, Barnett studied applied math and business, developing a stock-picking algorithm that he leveraged to form his Chicago-based hedge fund, SBB Research Group. Now he applies his mathematical and financial principles to his game. He knows, for example, not to get too excited about a high first-serve percentage—it means he probably isn't taking enough risks.

Kim and Jesse Witten, Barnett's friends, occasional doubles partners and tennis mentors, say Barnett has improved, particularly in volleying and in patience. Barnett, in turn, teaches them about finance. When they travel together, Barnett helps advise them on picking stocks. At 35, Kim has mostly retired from pro tennis and is pursuing his bachelor's degree at UCLA, planning a career in finance.

Their mutually beneficial friendship extends to getting into tournaments. Barnett's doubles ranking often is enough to get him into qualifying singles draws. But for doubles, his route usually is a wild card, secured with the help of Kim's and Witten's connections on tour.

Christian Forcellini, an organizer of the San Marino tournament, appreciates that Barnett and Becuzzi were willing to travel for a long-shot bid at a win; it meant the tournament had a full field for qualifying singles and didn't have to hand out byes. He isn't as sure what's in it for them. "I don't know if the tournament is the level for these players or if it's best they play the Futures," a level below Challengers on the circuit, he said.

Some on tour say they respect Barnett and Becuzzi for their perseverance. "They love tennis, love to travel," said American doubles specialist Nick Monroe. "They're living the dream."

Others aren't so charitable about Barnett. "He's a competent club-level player but nothing more, I think," said freelance tennis writer Stephen Kelly.

Phillip Simmonds, who beat Barnett, 6-0, 6-0, in Panama City last year, said Barnett should keep playing challengers as long as he can get into them. "He probably has a lot more resiliency than a lot of other guys," Simmonds said. "It's not easy to continue to lose and go out there and keep playing."

Kim worries about Barnett becoming notorious in tennis circles like American Will Ritter, an Atlanta-based singer who went 16-111 in low-level tournaments in the 1990s and 2000s. "I don't want that for Sam," Kim said.

Barnett said he'll keep traveling to tournaments that will have him, for as long as he is healthy and enjoying the sport. "It's humbling," he said. "There are always people better, and you can always get better."

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