Stan Wawrinka is aiming to rattle ice-cool Roger Federer in US Open
Stan Wawrinka believes he is one of the few players that makes Roger Federer nervous as the Swiss duo prepare to do battle in the US Open semi-finals.
Federer is yet to drop a set in five matches at Flushing Meadows, where he has continued his recent renaissance with a series of dazzling displays.
Richard Gasquet was the latest opponent to be blown away yesterday and of the four men left in New York, Federer now tops the tournament table for winners (26 per cent), return winners (15), first serves in (65 per cent) and service games won (97 per cent)..
During his 6-3 6-3 6-1 Gasquet demolition, Federer's watching father Robert was asked via commentary earpiece how many better performances he had seen his son play and he signalled for zero.
Aged 34, and the oldest player left in either the men or women's competitions, even Federer has been surprised by the standard of his performances.
"A little bit," Federer said. "And maybe at my age to run through five opponents the way I have done here at the US Open, I don't consider that normal, to be quite honest."
Admittedly, the 17-time Major champion showed similarly scintillating form at Wimbledon in July, beating Andy Murray in straight sets, before losing convincingly to Novak Djokovic in the final.
He was also resoundingly beaten by Wawrinka in the French Open quarter-finals in June, when his compatriot went on to outclass Djokovic in the final and win his second Grand Slam title. It marked a significant moment in the all-Swiss rivalry, largely because for a long time it was hardly a rivalry at all, with Federer stringing together 11 wins in a row against Wawrinka between 2009 and 2013.
More recently, however, Wawrinka has dented his compatriot's aura of invincibility, beating the World No.2 in Monte Carlo last year, stretching him in a tight match at Wimbledon, before finally demolishing him at Roland Garros.
"I think now we are both nervous when we enter the court. Before it was only me," Wawrinka said.
"I was nervous because I knew I wasn't at his level and now I think we can see that he is also nervous every time we have played each other in the past few years.
"That's a big difference because that shows how much he knows that I can play at his level, how much he knows I can try to play my game and not just try to react about what he's doing."
There was also the infamous row at the ATP Tour Finals in London last year when the duo reportedly engaged in a heated exchange after their match at the O2 Arena, in which Federer's wife Mirza heckled Wawrinka and called him a "cry baby".
Any animosity was quickly resolved, however, as the pair led Switzerland to Davis Cup glory one week later and mutual affection now appears completely restored, with one reporter asking Federer if there was even a brotherly feel to their matches.
Djokovic remains the favourite to lift the trophy in Sunday's final but the Serb must first overcome defending champion Marin Cilic in the last four.
Serena Williams' bid to reach the US Open final was put on hold as the women's semi-finals were rescheduled due to rain.
Williams takes on unseeded Italian Roberta Vinci and No.2 seed Simona Halep plays another Italian Flavia Pennetta.
Britain's Jamie Murray and Australian John Peers moved into the US Open doubles final.
Murray and Peers saved a match point to beat Americans Steve Johnson and Sam Querrey 6-4 6-7 (2-7) 7-6 (9-7).
It is the second successive Grand Slam final for Murray and Peers after their run at Wimbledon in July.