Paris (AFP)
Switzerland's Stan Wawrinka, suffering from a back injury, forged ahead of his quarter-final against compatriot Roger Federer in Basel on Friday after his victory over American Frances Tiafoe.
"The bad news is that I have to retire," said Wawrinka after his victory in two and a half hours over the American (6-3, 3-6, 7-5).
"I had problems with my back in the last match, I'm sure I will not get there tomorrow (Friday)." I'm going to retire, "added the Swiss, whose chances of qualifying for the Masters London are significantly lessened.
Already assured of his presence in London, Federer has previously sought a tenth title in Basel, his hometown.
In the semi-finals, he will face the winner of the quarter-op against Greek Stefanos Tsitsipas, who beat Ricardas Berankis, to the Serbian Filip Krajinovic, who got rid of Italian Fabio Fognini in two sets.
The other two quarters will be against Reilly Opelka of the United States and Roberto Bautista of Spain and Germany's Jan-Lennard Struff of Alex de Minaur of Australia
© 2019 AFP