Roger Federer rolling back the clock and ready to reach US Open final

Federer won the tournament every year between 2004 and 2008 but since then has found it a frustrating venue.

In 2009 he lost the final to Juan Martin del Potro, while in 2010 and 2011 he held match points against Novak Djokovic in the semi-finals only to lose both times.

The last two years have brought defeats by Tomas Berdych and Tommy Robredo before the last four, so it was no surprise Federer was particularly thrilled to achieve the feat in New York.

He said: "It's just unbelievable to win matches like this at slams. I have won other big ones in other places. But over best of five, saving match points against Gael in an atmosphere that it was out here, it's definitely very special.

"I'm not sure I have ever saved match point before in a slam. I'm unbelievably happy that it was now, because I knew I could play better after the first couple of sets."

In the semi-finals, Federer plays Croatian Marin Cilic, who is through to his second grand slam semi-final less than a year after serving a four-month ban for a doping offence.

Cilic used the time away from the game to focus on training and improving his game and is reaping the rewards.

"I feel I'm playing probably the best tennis of my career," said the 25-year-old, whose previous semi-final came in Australia in 2010.

"But I'm not getting satisfied too easy. I made it to the semis and it's completely different for me now than in 2010. At that time I was maybe a little bit too shocked and I didn't know how to deal with it afterwards. But now I'm cool and it's going well."

A big part of Cilic's resurgence has been the improvements he has made, particularly to his serve, under coach Goran Ivanisevic.

The cult of the former star as coach has reached its peak in New York, with all four men's semi-finalists being guided by former grand slam champions.

As well as Ivanisevic, Stefan Edberg is working with Federer, Boris Becker with Novak Djokovic and Michael Chang with Kei Nishikori.

Cilic said: "Probably the only matches I watched on TV were Goran's Wimbledon matches. That's my only memory from tennis at a very young age.

"And then later I started to play with him when I was 14. He was out due to his shoulder injury. That was huge to play with my idol.

"Goran is everything but not boring. We work a lot but some days we have sessions of three or three and a half hours, and we always have a good time. I would say it can't be better."

Djokovic is looking to reach a fifth straight final at Flushing Meadows having won the title in 2011 and lost twice to Rafael Nadal and once to Andy Murray.

The world number one takes on marathon man Nishikori, who has won back-to-back five-set matches against top-10 duo Milos Raonic and Stan Wawrinka.

The Raonic match finished at 2.26am, tying two other matches for the latest ever finish, but Nishikori was the only player to go on to win his next clash.

Djokovic said: "He's a very, very good player. I think he's playing the best tennis of his life in the last 12 months. He started working with Michael Chang and he changed a few things in his game. He serves very efficiently.

"Obviously he's very, very fast, maybe one of the fastest players on the tour. To be able to come back after winning against Raonic at 2.30am, again five sets, it's pretty impressive."

Nishikori is the first Japanese man to contest a grand slam semi-final since 1933, and no Japanese man has ever made a final.

The 24-year-old was a doubt even to play in the tournament because of a toe injury and admits his great run has taken even him by surprise.

"A little bit, yes," he said. "Because I didn't play much tennis. I was doing a lot of fitness training for two weeks before, but I wasn't hitting too much. I started to play points a few days before the tournament."

Nishikori has at least had two days to recover after the Wawrinka match, and he added: "My body is good."