Del Potro's upset victory over Roger Federer in Monday's U.S. Open final has put the Argentine city of 150,000 - lying in the foothills of a lowly mountainous area 400 kilometers (250 miles) south of Buenos Aries - on the map.
It has also brought attention to the club Independiente de Tandil, where Del Potro switched to tennis after growing up playing football, rugby union and basketball.
Marcelo Gomez, who taught Del Potro how to grip a racket and coached him until two years ago, said Del Potro used to walk by the club's tennis courts on his way to a football match. Eventually, he decided to give tennis a shot.
"Even then you could tell he had nerves of steel and great strengths," Gomez said. "His desire, his power and his concentration made me think that this child was going to stand out in tennis just like he did in football. He always wanted to play against others three or four years older - and he'd win. He is mentally very strong and that's why he beat Federer."
The 1.98-meter (6-feet-6) Del Potro is known at home, one of the few cities in Argentina where tennis is as popular as football, as the "Tower of Tandil." Growing up, his friends called him "Midget" and described his long, thin legs as "little sticks."
Because of his height and relative lack of mobility, Gomez said Del Potro worked on finishing off points quickly.
"He always played aggressively," Gomez said. "His size was going to limit his movement, so he always thought about the quick, hard-court game. His dream was the U.S. Open."
Everyone around the club seems to know Del Potro, who turns 21 next week.
"I played 1,000 times against him and only won once," said Bernardo Caballero, a tennis teacher at Independiente. "He was so angry. He never liked to lose, he was so competitive."
Perhaps the proudest person at the club is its president, Horacio Morrone.
"I watched him since he was young," Morrone said. "He was talented in football despite his height. He was a great goalscorer. If Juan Martin had stayed with football, he'd be a Maradona or Pele."
Tandil has produced other tennis players on the ATP circuit: Juan Monaco, Mariano Zabaleta, Maximo Gonzalez, Diego Junquiera and Guillermo Perez Roldan.
However, its biggest sports stars may be Spain and Atletico de Madrid defender Mariano Pernia and Mariano Gonzalez, who won Olympic gold in 2004 in football.
Like the city, Del Potro's family is comfortable yet not prone to publicity. His father Daniel is a veterinarian and mother Patricia a literature teacher, while he gave his 18-year-old sister Julieta a luxury car he won last year in a tournament in Stuttgart, Germany.
Tandil's other claim to fame was the "Moving Stone," a large boulder which balanced on a ledge without falling - until it toppled in 1912. It has since been replaced with a duplicate stone that has also become famous.
"Now, Tandil won't be known only as the city of the Moving Stone," said Raquel Cingolani, who works in a clothing shop in the city. "Now, Tandil is the city of Del Potro."
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