Croatia's Marin Cilic overwhelmed 17-time Grand Slam champion Roger Federer 6-3, 6-4, 6-4 on Saturday to book an unlikely US Open final against Japan's Kei Nishikori.

The 14th-seeded Cilic, who missed last year's US Open as he served a doping ban, reached his first Grand Slam final, denying the 33-year-old Federer's dream of a sixth title in Flushing Meadows.

Marin Cilic
Marin Cilic. Pic/AFP

It will be the first major final that has not featured one of the big three of Djokovic, Federer or Rafael Nadal since the Australian Open final in 2005 when Marat Safin defeated Lleyton Hewitt.

Cilic, who missed the 2013 US Open as he sat out a doping ban, overwhelmed 17-time Grand Slam champion Federer with 13 aces and 43 winners.

The second seeded Swiss, the champion between 2005 and 2008, was bidding at 33 to become the oldest winner of a Grand Slam title in more than 40 years and vying to reach a seventh final in New York.

Instead, he was out-played by the 25-year-old Cilic, ranked 16th in the world, whose only prior appearance in a major semi-final was at the 2010 Australian Open.

Federer had come from two sets to love down and saved two match points in his quarter-final win over Gael Monfils, but there would be no astounding escape this time.

"To be able to play like this, I never dreamed of," said Cilic. "I think today was just the best performance ever in my career."

He's the first Croatian to reach a Grand Slam final since Goran Ivanisevic, now Cilic's coach, won Wimbledon in 2001.

Federer said he wasn't affected by his five-set marathon against Monfils.

"I was feeling fine. I just think if I could have stayed longer with him in the first set, I felt like there was a proper match going on," said the Swiss.

"But I think him playing with the lead he played with -- no fear and just full-out confidence, which clearly everybody at this point sort of has in the semis of a slam.

"I think Marin played great. I maybe didn't have my best day, but I think that was pretty much it in a nutshell."