Roger Federer plans on working on his game
Federer beat Alexander Zverev 7-6 5-7 6-1 last night to seal a place in the last four.
It leaves Zverev with a must-win match against Jack Sock tomorrow with a semi spot at stake.
Now Federer, who is gunning for his seventh ATP Finals win, will use his time to sharpen his game.
He said: "It was a tough battle and I am extremely happy to be through.
Roger Federer has reached the last four of the ATP Finals
"It has been a tough group, so to get through in two matches is great.
"Now I can maybe work on my game a little bit."
Roger Federer faces Marin Cilic tomorrow in a dead rubber at the O2.
He added: “I’m happy and relieved that I can play freely against Cilic, instead of it being a nail-biter.”
ATP World Tour Finals odds: Who will win at the O2?
Tue, November 14, 2017
Express Sport runs through the odds for the ATP World Tour Finals at the O2 Arena (Odds provided by Sky Bet, accurate as of 14/11/17)
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Who is favourite to win the ATP World Tour Finals at the O2 Arena?
Federer, 36, was praised by Sky Sports pundit Greg Rusedski for his movement in the win.
“Lots of people watch Federer and says he glides around the court, but if you cut off the top half and watch his feet,” Rusedski said.
“His feet move so quickly and you can see the difference in the third set.
“It was a big change.”