Japan's world number seven, who has now won all five of his meetings with Kazakhstan's Kukushkin, reached his first ATP semi-final since Tokyo in October.

He'll face fourth-seeded American Sam Querrey in a rematch of their semi-final clash here last year.

Querrey ended the dream run of Japanese qualifier Yoshihito Nishioka 6-3, 6-4.

Although he emerged with the straight-sets win, Querrey said it wasn't easy against the Japanese left-hander.

"We had a lot of close games, it was a tough match," said Querrey, who served up 11 aces and saved both break points he faced to win in 72 minutes -- ending Nishioka's dream of facing compatriot Nishikori.

In Saturday's other semi-final, 18-year-old American Taylor Fritz will battle Lithuania's Ricardas Berankis.

Fritz, ranked 145th in the world, upset second-seeded Steve Johnson on Thursday and followed up with a hard-fought 6-4, 5-7, 7-6 (7/5) victory over Germany's Benjamin Becker.

Becker served for the match at 6-5 in the third set, but Fritz broke him to force the tie-breaker.

"It's incredible, I can't believe it," Fritz said. "To come back in that way, with him serving for the match, I'll never forget that."

Fritz fired 13 aces and saved six of the 11 break points he faced in the two-hour, 20-minute duel.

Berankis, ranked 102nd in the world, advanced with a 7-6 (7/3), 6-1 victory over third-seeded American Donald Young.

"Maybe it wasn't Young's best day today," said Berankis, who reached his second career ATP semi-final. "He didn't really have a plan B and thought I would put myself in trouble with fast shots and mistakes, but it didn't work out for him."