In an astonishing reversal of fortunes, the 33-year-old, written off as a relic of the game when he slipped to a fourth round loss to Tommy Robredo in 2013, is perfectly positioned to win a staggering 18th major at the season's concluding Grand Slam event which starts Monday.
Buoyed by claiming a sixth Cincinnati title and his 80th career crown, the Swiss is revelling in the twilight of his career just a year after it was being consumed by darkness.
The defeat also marked the first time in 10 years that he hadn't made at least the last-eight at Flushing Meadows.
Suddenly, his five consecutive US Open titles from 2004-2008 appeared a detail in history and his 17th and most recent major success -- the 2012 Wimbledon title -- looked certain to be his last.
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But the Swiss never doubted his ability to remain a force in the sport and he goes into his 15th US Open with his unwavering confidence justified.
Since then, he has been runner-up at Toronto and champion in Cincinnati.
"I come in with great confidence," said Federer, chasing a record sixth title in New York and where he will be playing in a 64th consecutive Grand Slam.
"I know my game is where I want it to be. It's about just keeping that level up right now."
Meanwhile, his fellow members of the "Big Four" are slipping and sliding.
Djokovic, the 2011 champion, heads into the tournament with two dispiriting third round losses in Toronto and Cincinnati with the 27-year-old Serb, recently married, having to bat back accusations that he is distracted by impending fatherhood.