Results, titles, prize money and rankings all tell the story of a player’s rise through tennis. But there are other signs too — and in recent years, it has become a pretty good idea to take notice if certain fashion brands decide to bring someone on board.

Iga Świątek was already the world No. 1 when On, the Swiss company that counts Roger Federer as a major investor, signed her in a head-to-toe deal in March 2023. But Ben Shelton, who signed simultaneously, was just out of college and making his way through his first full season on the ATP Tour.

Italy’s Flavio Cobolli was struggling to compete with top players when he joined; rising star João Fonseca was another early bet. And all of them are now established players, whose best years should still be ahead of them.

Joining them is a fully fledged star of another racket sport: padel. Arturo Coello, the 21-year-old world No. 1 from Spain, is the company’s first signing in a fast-growing sport that is well behind tennis as a spectator sport, but in other ways, including player media and the embrace of fan-generated content, is moving ahead of it.

For the uninitiated, padel is a combination of racketball, squash and tennis, a doubles game on a small court surrounded by perspex walls that are in-bounds as long as the ball hits the ground first. It’s more friendly to beginners than tennis, and less sedentary than pickleball. It has become a sport for athletes in other sports and for celebrities, as well as a recreational phenomenon which is now moving toward the U.S.

Four years ago, there were just 180 courts in the U.S. The U.S. Padel Association forecasts 30,000 courts by 2030, but planning permission can be difficult to acquire because of noise and there are currently around 700. There are around 270,000 tennis courts.

Coello, whose country is at the center of padel’s universe and has been for some time, is ahead of the curve.

“On is very, very young in terms of the brand and I’m very, very young, in terms (of being a) professional player, so we are combining a lot of things,” he said during an interview earlier this week.

Terms of the deal were not disclosed, but the company plans to release a new padel shoe to the market, with his collaboration, in 2027.

Feliciano Robayna, the head of athlete management for tennis at On, said in an email that Coello’s “journey to becoming the youngest-ever world No. 1 has a lot of parallels with our own story of disrupting an industry.”

Coello, who grew up in Valladolid, roughly 100 miles north of Madrid, spent his childhood playing mostly tennis, soccer and padel. He started focusing seriously on the latter at 10. At 16, he decided his prospects were the best in that sport. He told his parents he wanted to pursue a pro career and hasn’t looked back much since then, though the decision came with some consequences, including figuring out how to balance the two lives that nearly every athlete wants to experience.

“One life is very nice, you are famous, you live around the world, you travel a lot, you’re a professional of your sport,” he said. “But you need to say no to a lot of things and normal themes and. I remember when I was 16, 17, and all my friends go to a party or were doing something like this.

“And I say, ‘I need to go to home, to rest, to be focused because my life is over and we need to be a professional. Yes, we have a very good part and you have also a bad part.”

Coello is friendly with men’s tennis world No. 1 Carlos Alcaraz, who has documented similar push-and-pull in his journey to the top. Alcaraz is one of Nike’s top tennis athletes, which is yet to make a serious play in padel. Coello said he was drawn to On in part because of Shelton, the brash young American with the explosive serve, dynamic game, and exuberance on the court.

“He’s lefty like me and I like his style,” said Coello, who has a similar head of bushy brown curls.

“I see his profile and say, ‘OK, it’s a good idea for me to be part of this brand.’”

During an interview last year, Shelton said that part of his motivation in joining On was that he “didn’t want to be one of 50 Nike guys.”

The business of fashion in tennis is increasingly a parable of fishes in ponds. Players who aren’t worldwide superstars, like Świątek, can either be dwarfed by them at the biggest labels — like Alcaraz and women’s world No. 1 Aryna Sabalenka’s power at Nike — or be bigger fish at smaller labels. Coello is first in at On, and the world No. 1 is swimming alone.