Many may be surprised by Roger Federer's untroubled progress towards becoming the oldest US Open champion in almost half a century, but not Federer himself.
The 34-year-old has glided into the semi-finals, where he will face Swiss compatriot Stan Wawrinka on Friday.
It will be his 10th New York semi-final as the five-time champion targets a record sixth US Open and 18th Grand Slam title.
"For many years I have tried to look at the big picture to hopefully still be playing at a high level at this age," said Federer, who would be the oldest winner of the US Open since Ken Rosewall in 1970.
"So in some ways I am not surprised I am playing as well as I am."
Federer has not won a major since his seventh Wimbledon title in 2012, but came into the US Open on the back of a seventh Cincinnati title, defeating world number one Novak Djokovic in the final.
It was his 87th career title and pushed his on-court earnings to almost USD 94 million.
His form in New York has been just as impressive, dropping serve just twice and not yet having lost a set.
Despite his Grand Slam title drought -- the longest of his career -- Federer has not been afraid to keep innovating.
In recent years, he has experimented with a larger racquet, brought in former world number one Stefan Edberg to work alongside long-time coach Severin Luthi and radically altered his playing schedule.
The US Open is only his 13th tournament of the year.
He has also invented a new tactic, the 'SABR' or 'Sneak Attack By Roger,' which is his chip-and-charge on an opponent's second serve.
After his 87-minute quarter-final demolition of Richard Gasquet on Thursday, Federer also said he was sleeping more -- up to 10 hours a day -- to maintain his competitive level.
"I think I have worked on my game moving forward, have been able to take the ball earlier," he said when asked to explain his longevity.
"I think I'm volleying better than I have the last 10 years. It's all about keeping yourself in shape and staying injury-free. And motivated.
"I've played so well over the last one-and-a-half years. I don't feel like I'm as old as I am. I still feel young."
He has come close to adding to his 17 majors.
He made the final at Wimbledon in the last two seasons, only to be denied on both occasions by Djokovic.
Federer's stunning semi-final rout of Andy Murray at the All England Club also had the sport drooling.
At this year's US Open, Federer has seen world number three Murray knocked out in the fourth round as the British star saw his run of 18 consecutive Grand Slam appearances come to an end.
Old nemesis Rafael Nadal fared even worse, a third-round loss his earliest exit in a decade.
The threat from Djokovic, who plays defending champion Marin Cilic in Friday night's other semi-final, remains real.
However, the Serb has endured a rollercoaster tournament, needing four sets to see off Spaniards Roberto Bautista Agut and Feliciano Lopez.
The odds are on a potentially classic final between Australian Open and Wimbledon winner Djokovic and Federer on Sunday.
It will be too tight to call.
They have met 41 times with Federer leading 21-20.