Milor Raonic, Novak Djokovic, Serena Williams and Madison Keys all in action
Novak Djokovic of Serbia stretches for a backhand in his quarter-final match against Milos Raonic of Canada during day 10 of the 2015 Australian Open at Melbourne Park on January 28, 2015 in Melbourne.Scott Barbour/Getty Images
Television cameras are seen as Milos Raonic of Canada serves against Novak Djokovic of Serbia during their men's singles quarter-final match at the Australian Open.BRANDON MALONE/Reuters
Milos Raonic hits a return against Novak Djokovic during their men's singles match.MAL FAIRCLOUGH/AFP / Getty Images
Novak Djokovic slips and falls over as he chases the ball in his quarter-final match against Milos Raonic.Scott Barbour/Getty Images
Milos Raonic of Canada stretches to hit a return against Novak Djokovic of Serbia during their men's singles quarter-final match at the Australian Open 2015 tennis tournament in Melbourne.THOMAS PETER/Reuters
Serena Williams shouts during her women's singles match against Slovakia's Dominika Cibulkova.WILLIAM WEST/AFP / Getty Images
Serena Williams of the U.S. reacts after missing a point against Dominika Cibulkova of Slovakia during their women's singles quarter-final match at the Australian Open.BRANDON MALONE/Reuters
Dominika Cibulkova of Slovakia serves in her quarter-final match against Serena Williams.Clive Brunskill/Getty Images
Serena Williams celebrates defeating Dominika Cibulkova of Slovakia to win their women's singles quarter-final match.CARLOS BARRIA/Reuters
Spectators wearing hats watch as Madison Keys of the U.S. hits a return to compatriot Venus Williams during their women's singles quarter-final match at the Australian Open.BRANDON MALONE/Reuters
Venus Williams of the serves during her women's singles match against Madison Keys.WILLIAM WEST/AFP / Getty Images
Madison Keys of the U.S. hits a return to compatriot Venus Williams during their women's singles quarter-final match at the Australian Open.CARLOS BARRIA/Reuters
Spectators watch as Venus Williams of the U.S. serves to compatriot Madison Keys during their women's singles quarter-final match at the Australian Open.BRANDON MALONE/Reuters
Venus Williams of the U.S. casts a shadow as she serves to compatriot Madison Keys during their women's singles quarter-final match at the Australian Open.CARLOS BARRIA/Reuters
Japan's Kei Nishikori plays a shot during his men's singles match against Switzerland's Stanislas Wawrinka.MAL FAIRCLOUGH/AFP / Getty Images
Stan Wawrinka of Switzerland stretches out for a return to Kei Nishikori of Japan during their quarter-final match at the Australian Open.Lee Jin-man/The Associated Press
A supporter of Stan Wawrinka of Switzerland yells as he plays Kei Nishikori of Japan in their men's singles quarter-final match at the Australian Open.BRANDON MALONE/Reuters
Switzerland's Stanislas Wawrinka plays a shot during his men's singles match against Japan's Kei Nishikori.GREG WOOD/AFP / Getty Images
A general view as Kei Nishikori of Japan is aced in his quarterfinal match against Stanislas Wawrinka of Switzerland.Scott Barbour/Getty Images
A detail of tennis balls as Stanislas Wawrinka of Switzerland chooses which ball to serve with in his quarterfinal match against Kei Nishikori of Japan.Scott Barbour/Getty Images
The shadows of Kei Nishikori (top) of Japan and Stan Wawrinka of Switzerland are seen as they shake hands after Nishikori was defeated in their men's singles quarter-final match at the Australian Open.CARLOS BARRIA/Reuters