(REUTERS) - Kei Nishikori withstood a blistering early assault and saved five match points before battling past Frenchman Gael Monfils 4-6, 6-3, 7-6 (7-3) in a bruising quarter-final at the Miami Open on Thursday.

The Japanese will face 24th seed Nick Kyrgios in the semi-finals after the Australian upset 12th seeded Canadian Milos Raonic 6-4, 7-6 (7-4).

Sixth seed Nishikori appeared to have his match in control when leading 4-2 in the final set but his usually reliable forehand repeatedly let him down.

He saved four match points in that 10th game, and a fifth in the 12th, before racing into a 6-3 lead in the tiebreak as Monfils made a string of unforced errors, Nishikori finally sealing the win with a forehand crosscourt winner.

"When I was down 4-5 and 0-40, I thought I almost gave up the match," Nishikori, 26, told ESPN in a courtside interview after an epic encounter between two of the most athletic players on the ATP World Tour that lasted 21/2 hours.

Nishikori, who also reached the last four in Miami two years ago, was left reeling in the opening set as the 16th-seeded Monfils played high-risk, aggressive tennis right from the start, highlighted by an explosive service game.

"I was a little bit surprised how he played, especially the first couple of games," said Nishikori.

Meanwhile, Kyrgios took down his more fancied opponent in two sets to reach the last four for the first time in a ATP Masters 1000 event, riding a break in the first game of the match all the way to victory.

"I knew it would be a tough match. Milos has played great the last couple of weeks and the only person he's lost to is Djokovic so I knew it would be a tough task," Kyrgios said.