Kei Nishikori called his loss at Monday's U.S. Open final an important step in his career when he arrived in Japan on Saturday.
"The frustration of losing the final was big, but it marked my taking a big step in my tennis career," Nishikori told a news conference after arriving at Narita Airport.
"I feel I am just a little bit closer to achieving my dream of becoming No. 1 in the world."