Swiss tennis star Roger Federer made headlines two weeks ago when he appeared on center court at Wimbledon wearing an outfit bearing the red-and-white squares of Uniqlo, the signature brand of Japanese apparel maker Fast Retailing Co.

Fast Retailing did not reveal the details of its contract with the 36-year-old, but on the day of the match said he had become one of its "global brand ambassadors," a title shared by fellow player Kei Nishikori and Australian golfer and 2013 Masters champion Adam Scott.

Until the announcement, Federer, a Nike Inc. client for over two decades, was reportedly wearing unbranded tennis wear during warm-ups and a Nike shirt in the locker room when the tournament opened on July 2.