TOKYO (AFP) - Defending champion Kei Nishikori survived a war of attrition against Croatia's Marin Cilic to reach the Japan Open semi-finals on Friday, winning a cliffhanger 3-6, 7-5, 6-3.

Top seed Stan Wawrinka overpowered American qualifier Austin Krajicek 6-3, 6-4 to join him in the last four, though the Swiss required less than an hour to take care of business on a sunny afternoon in Tokyo.

Second seed Nishikori was greeted like a rock star by 12,000 screaming fans but Cilic, who beat Japan's golden boy in last year's US Open final, had failed to read the script and quickly seized the initiative with some thunderous hitting.

Serving with such ferocity he knocked the racket out of Nishikori's hand, the sixth seed broke first with a thumping forehand drive to lead 4-2 before wrapping up the opening set with an ace down the centre.

Nishikori is a tough nut to crack on the Tokyo hardcourts, however, having captured the Japan Open twice in the last three years.

And when cracks began to appear in Cilic's armour, he levelled with an acrobatic leaping backhand that the lanky Croat could only dump into the net.

Cilic's game unravelled under the onslaught in the decider as Nishikori caught fire, breaking for 3-1 and closing out the quarter-final with an ace after two hours, 11 minutes to ensure "Nishikori Fever" stretches into the weekend.

"When I drove past all the fans on the buggy after practice this morning, I thought: 'This is what it must feel like to be a lion in a zoo'," joked Nishikori, who is regularly mobbed on his return to Japan. "The wind made it difficult today but I hung in and waited for my chances."

"I had a couple of dangerous moments out there but that happens."

Nishikori, bidding to win a fourth title of the year, next faces Benoit Paire - the man who stunned him in the first round of this year's US Open - after the Frenchman beat volatile Australian Nick Kyrgios 3-6, 6-4, 6-1.