Fast Retailing Co. is ready for war. The clothing maker's battle begins Saturday, when world No. 1 Novak Djokovic takes on 10th-seed Kei Nishikori in the U.S. Open semifinal.

Billionaire founder Tadashi Yanai wins, regardless of the outcome. Both players, signed on in the last three years, will be wearing his Uniqlo brand clothes at the final Grand Slam of the year in New York. Nishikori made history Wednesday, beating third-seed Stan Wawrinka to become the first Japanese man in 96 years to reach the U.S. Open semifinals.

"It's a Uniqlo war on one court," said Eriko Muteki, a spokeswoman for the brand. "It's fantastic for us to have both of these stars battling each other while wearing our clothes."