Australian Open quarter-finalist Kei Nishikori has said he was responsible for Japan's first round exit from the Davis Cup this weekend after his defeat by Croatia's big-serving giant Ivo Karlovic.
"I was the one who had to put up two wins for my country," Nishikori told Japanese media on Sunday after his teammate Go Soeda bowed to Karlovic in a decisive fifth match in the Japan-Croatia tie in Hyogo, western Japan.
"Given the fact I didn't get two wins here, I definitely have more room to improve," he said, according to Kyodo news agency.
Nishikori, the highest-placed Japanese man in world rankings history at 20th, was demolished by No. 43 Karlovic 6-4, 6-4, 6-3 in the opening singles match on Friday. But the Japanese ace beat Ivan Dodig 7-5, 7-6, 6-3 on Sunday.
Karlovic, 208 centimetres (6 feet 10 inches) tall, whipped both Nishikori and Soeda in straight sets without facing one breakpoint on his serve. He also combined with Dodig to beat a separate Japanese duo in Saturday's doubles.
"I'll try to become a player who can always win both of my two matches in a Davis Cup series," said Nishikori, who has upset some of the world's top players in recent months.
The 22-year-old beat world No.1 Novak Djokovic to reach the final of the Swiss Indoors last November. He shocked No. 6 Jo-Wilfried Tsonga in the fourth round before losing to Andy Murray at the Australian Open last month.
Nishikori became the first Japanese man to reach the quarter-finals of a Grand Slam tournament since Shuzo Matsuoka did so at Wimbledon in 1995.
"Karlovic singlehandedly knocked us out," Japan captain Eiji Takeuchi said. "He dominated us with his serve-and-volley game as well as consistent groundstrokes. My players had little chance against him. He was playing almost perfectly this week."
Croatia captain Zeljko Krajan said: "With the way Ivo played at the moment, it would be tough for any team to beat Croatia."
"When he is confident even from the baseline, it makes things tough for any team."
Japan were playing in the Davis Cup top-tier group for the first time in 27 years. They face a promotion-relegation playoff in September.