Stan Wawrinka was forced to withdraw from today’s quarterfinal showdown against best friend Roger Federer with a back injury, just an hour after struggling past America’s Frances Tiafoe in a gruelling second round clash at the Swiss Indoors .

“The bad news is that I will have to retire,” the 34-year-old three-time Grand Slam winner said after his 6-3 3-6 7-5 win. “I had some trouble with my back in the last game. I’m sure I cannot make it for tomorrow.” Top seed Federer, chasing a 10th title at his hometown event, will receive a walkover into Saturday’s semifinals.

It would have been the 27th meeting between the two Swiss teammates and Federer would have been the comfortable favourite boasting a 23-3 record over their 14-year rivalry.