Paris (AFP) - Japan's Kei Nishikori believes his rise into the world top five would never have happened had he not forged his skills in America's do-or-die sports environment.
Nishikori left his home and family in Shimane when he was just 14 with no English skills, just a passionate belief that he could become Japan's most successful tennis player.
A decade later, he was the first Asian man to reach a Grand Slam final, losing to Marin Cilic in the US Open title match having knocked out Novak Djokovic on the way.
Also the highest-ranked Japanese man in the history of the sport, Nishikori says he is indebted to his life and work in Florida.
"I got really strong living in the States, because I wasn't mentally really strong and I wasn't really like the fighter when I was little," said Nishikori after seeing off Brazil's Thomas Bellucci 7-5, 6-4, 6-4 to make the third round of the French Open on Wednesday.
"When I moved to U.S., you have to be stronger somehow, and a lot of kids from different countries and sometimes you have to play with big guys, especially I was small when I was little.
"When you have to play a lot of tournaments and you get more experience and you get more confidence playing a lot of matches, and also you get mentally strong."
Seeded fifth at Roland Garros this year, the 25-year-old Nishikori has reached the third round for the second time.
It's a tournament which has also reflected his career achievements -- when he made the last 16 in 2013, he became the first Japanese man to play in the fourth round since Fumiteru Nakano in 1938.
This year, he is happy to progress beneath the radar with the focus almost exclusively on Djokovic, Roger Federer, Rafael Nadal and Andy Murray.
And he is no stranger to clay success -- last year he was runner-up to Nadal in Madrid while he has already defended his claycourt title in Barcelona this season.
"This year I think I'm feeling comfortable and very confident, and my body is good," said Nishikori, who faces Germany's Benjamin Becker for a place in the last 16.
He's also proving an inspiration for other Japanese male players -- at Roland Garros this year, five men started out in the main draw, the most since 1967.
"It's an honour to be Japanese. I am the number one Asian player and many kids start playing tennis in Japan."