After his best season as a pro, world No. 5 Kei Nishikori believes he can ascend higher in the rankings. The Japanese player reached his first Grand Slam final at the U.S. Open, which he lost to Marin Cilic.

"I was really disappointed I couldn’t play good tennis in the final because I was playing really well for two weeks and then in the last match I couldn’t,” he told Reuters. “But I needed a little more experience as I got a little bit tight in the final. Marin played really great tennis so I couldn’t really do much.

“But after that I won two tournaments in Asia. The next goal is to win a Grand Slam but I know it’s not easy to go even to the semis or final, so it may take some time but hopefully I can reach a Grand Slam final again."

Back in 2008, Nishikori was ranked No. 45 to become his country’s highest-ranked player ever. Nishikori could climb to No. 4 defending on his performance at the ATP World Tour Finals. He  says he does eventually want to reach No. 1.

"I hope so,” he said. “I want to beat my best ranking for sure."