Defending champion Kei Nishikori survived a courageous ambush attempt from Croatian teenager Borna Coric to reach the second round of the Japan Open on Monday.

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Playing his first match since helping Japan preserve their place in the Davis Cup world group with victory over Colombia last month, second seed Nishikori had to work extremely hard for his 2-6, 6-1, 6-2 win in Tokyo.

Coric, who stunned Andy Murray in Dubai earlier this year, threatened to spring another upset after exploding from the blocks to take the first set, sealing it with a vicious kick serve which forced Nishikori into a wild return.

But Nishikori, who currently features in a Japanese television commercial for instant noodles dressed as a samurai and smashing a hapless blond-haired opponent with a sword instead of a racquet, awoke from his slumber just in time.

He came roaring back to take the second set before finishing the job in brutal fashion — an ace to give him match point and a huge serve to the body, flooring the 18-year-old Coric. 

“He made it hard for me at the start,” said the world number six, who has owned the Tokyo centre court in recent years, winning two of the last three Japan Open crowns. “I knew what I was doing wrong and it was a question of cutting down on the errors,” added Nishikori, chasing a fourth title of the year and the 11th of his career. 

Nishikori, who has won titles in Memphis, Barcelona and Washington this year, will take on big-serving American Sam Querrey in the last 16 after he beat Ukraine’s Alexandr Dolgopolov 7-6, 6-4 in an absorbing first-round match.

“It will be another tough match and I know I will need to be careful with his serve,” said Nishikori. “But I’m happy to get past the first hurdle and hopefully I can get on a roll and play better as we get closer to the weekend.”

Switzerland’s French Open champion Stan Wawrinka, who heads a quality field in Tokyo, opens his bid against Czech Radek Stepanek on Tuesday.

Wawrinka will not be relishing his second-round match if he deals with Stepanek, however, as the world number four would play Japan’s Tatsuma Ito, the player who dumped him out of the tournament in the first round last year.