On Thursday Federer suffered his latest shock defeat against Daniel Brands in the second round while second seed Wawrinka retired in the quarter-finals on Friday.
Federer blamed his loss partly on his troublesome back, and a back problem was also reportedly Wawrinka's reason for pulling out while trailing Feliciano Lopez 6-4 2-6 4-3.
Fifth seed Lopez meets Dutchman Robin Haase in the last four after he defeated Marcel Granollers 7-5 in a deciding tie-break.
Upsetting Federer was as good as it got for Brands, the German losing 6-3 6-4 to Romania's Victor Hanescu on Friday, and he will take on Mikhail Youzhny next.
The Russian sixth seed saw off fourth seed Juan Monaco in a very tight match, saving three match points before clinching a 5-7 6-4 7-6 (9/7) victory.
Meanwhile, Britain's Jamie Murray will contest the doubles final with Australian partner John Peers after the pair defeated another Briton, Jamie Delgado, and Facundo Bagnis 6-1 6-4 on Friday.
Murray and Peers meet Spaniards Pablo Andujar and Guillermo Garcia-Lopez in Sunday's decider.