At the end of a frustrating season by his own high standards, Federer seems to have saved his best until last and has ripped through his three round-robin matches with the air of a man who has a point to prove.
David Ferrer, Andy Murray and Robin Soderling are all ranked in the world's top eight but none could even take a set off Federer in the prestigious end-of-season event at London's O2 Arena this week.
This was Federer at his sublime best. On Thursday, Soderling was desperate for the win he needed to make the semi-finals and came at Federer with all guns blazing, but the Swiss star had the answer to everything his opponent threw at him.
Yet Federer, who has won this event four times, knows his hard work in the group stage will be wasted unless he leaves London with the title.
He could face either Rafael Nadal, Novak Djokovic or Tomas Berdych in Saturday's semi-finals, depending on their Group A results on Friday, and expects a stern examination.
"I'm still two matches away (from winning the title), two really tough matches. I'm most likely going to play against top five guys," Federer said.
"It depends who I play, I don't even know yet but it's going to be a tough weekend ahead of me. That's my focus right now.
"So far it's been good. I won against top 10 players in straight sets. That's going to make me feel obviously awfully good for the weekend. But I hope I can keep it up.
"The tournament's not over yet. This is really when it starts for me."
It has been a curious year for Federer. After winning the Australian Open in January, he went nine tournaments without a title until landing the Cincinnati Masters in August.
The anguish of failing to defend the French Open and Wimbledon titles, as well as losing the number one ranking to Nadal has nagged away at him for months.
But, while many pundits claim Federer has lost some of his hunger, the 29-year-old is adamant he has every reason to be satisfied with his year's work.
"I won the Australian Open right off the bat at the beginning. That kind of keeps you going for a few months. Then you sometimes lose close matches, that can happen," he said.
"I had a lung infection in February. I only played a handful of matches all the way to Madrid really. You can't really say I was playing horrible. I was just losing some close matches.