Roger Federer fought back from a set down to beat Croatia’s Marin Cilic and end the group stage unbeaten.
The world no. 2 who had already secured semi-final qualification after beating Jack Sock and Alexander Zverev in the Boris Becker group , edged Marin Cilic 6-7 (5-7) 6-4 6-1.
“Knowing I was qualified on Tuesday evening – it’s kind of weird to be already through to the semis, but of course it gives me a great idea how I want to prepare for Saturday,” said Federer.
“One more last weekend, one more push before the vacation and then preparation for the next season.”
This will be Roger’s fourteenth semifinal in fifteen appearances at the tournament and, on Saturday, he will play either David Goffin or Dominic Thiem from the Pete Sampras group.
Marin Cilic, meanwhile, bows out without a single win as his poor record in the season-ending tournament continues.