Asia's highest-ranked tennis player, Kei Nishikori, has renewed his endorsement deal with Fast Retailing Co.'s Uniqlo clothing brand.

"I have been impressed at how he has continued to evolve as a player," Fast Retailing chairman Tadashi Yanai said in a statement about the contract Friday. The deal may exceed $10 million a year, according to a person familiar with the agreement.

The 26-year-old Japanese made history at the 2014 U.S. Open by becoming the first Asia-born man to reach the finals of a Grand Slam tournament. Nishikori's success vaulted him to fame and helped him win endorsements from the likes of Jaguar, TAG Heuer and Japanese construction materials maker Lixil Group Corp., a sponsor of the 2020 Tokyo Olympics.

Olivier van Lindonk, Nishikori's agent, declined to comment on the terms of the agreement with Uniqlo, which initially named Nishikori a "global brand ambassador" in 2011. Van Lindonk said the Olympic Games bode well for his client, the youngest player currently ranked in the top 10.

"Companies are looking for the next generation of champions," said van Lindonk, vice president of tennis at talent-management agency IMG . "With Tokyo 2020 only four years away, this created an interesting dynamic with the clothing companies looking for an Asian star."