Federer became the first player to qualify for the last four at this year's season-ending event thanks to a 6-4, 7-6 (7/5) victory over Spain's David Ferrer on Thursday and the world number two looks in ominous form as he eyes a seventh Tour Finals title.
Few players have ever been more at home on the indoor courts than Federer and once again he is thriving under the domed roof of the O2 Arena in south-east London, where he has won the Tour Finals for the last two years.
In total, Federer has won 20 indoor titles during his illustrious career and the 31-year-old admits he is more comfortable than most playing under roofs after growing up on covered tennis courts.
"Indoors I've been very successful over the years. Probably won the most titles indoors, maybe more than all the other guys combined," Federer said.
"The margins actually are smaller indoors normally because a guy can really
get hot, can serve well.
"But I think indoors is a natural surface for me. So is clay actually, because those were the two surfaces I grew up on.
"In the summers, I used to play on the clay courts outdoors, and in the winters, I played indoors on carpet, when I was young. I guess this is where it kind of comes through a little bit for me.
"I also had my first success on the tour actually indoors back in Marseille and Rotterdam and Basel and Toulouse.
"Outdoors I'm actually amazed how good I've become in the wind and humidity.
"That, for me, was the tough part, actually becoming a good player in those conditions."
Federer's win over Ferrer clinched his 10th semi-final berth in his last 11 appearances at the season-ending event, leaving him with a dead rubber to come against Juan Martin del Potro on Saturday.
But the 17-time Grand Slam champion has no intention of taking it easy against the Argentine, who stunned Federer in the final of the Basle Open last month.
"I'm playing great," Federer said.
"But I see also other players this week playing wonderful tennis," he said.
"Now I'm into the semis, so that's a bit of a relief. I know I've got a chance so we will see how it plays out.
"I can already maybe then work on my game in the next match (against del Potro) looking ahead to the semi-finals, which is a good thing."