Supporters of Japanese tennis player Kei Nishikori cheer while watching the US Open tennis semifinal match at Nishikori's home town of Matsue on September 7, 2014. (Photo credit should read JIJI PRESS/AFP/Getty Images)
2014 US Open - Day 13
Roger Federer of Switzerland walks down a hallway to the court prior to a game against Marin Cilic of Croatia in their men's singles semifinal match on Day Thirteen of the 2014 US Open at the USTA Billie Jean King National Tennis Center on September 6, 2014. (Photo by Chris Trotman/Getty Images for USTA)
2014 US Open - Day 13
Marin Cilic of Croatia celebrates after defeating Roger Federer of Switzerland during their men's singles semifinal match on Day Thirteen of the 2014 US Open at the USTA Billie Jean King National Tennis Center on September 6, 2014. (Photo by Chris Trotman/Getty Images for USTA)
2014 US Open - Day 13
Roger Federer of Switzerland leaves the court after being defeated by Marin Cilic of Croatia during their 2014 US Open men's semifinal singles match at the USTA Billie Jean King National Tennis Center on September 6, 2014. (Photo credit should read STAN HONDA/AFP/Getty Images)
2014 US Open - Day 13
Marin Cilic of Croatia celebrates his win over Roger Federer of Switzerland during their 2014 US Open men's semifinal singles match at the USTA Billie Jean King National Tennis Center. (Photo credit should read STAN HONDA/AFP/Getty Images)
2014 US Open - Day 13
Kei Nishikori of Japan celebrates after defeating Novak Djokovic of Serbia in their men's singles semifinal match on Day Thirteen of the 2014 US Open at the USTA Billie Jean King National Tennis Center on September 6, 2014. (Photo by Julian Finney/Getty Images)
2014 US Open - Day 13
Novak Djokovic of Serbia waves to the crowd after being defeated by Kei Nishikori of Japan in their men's singles semifinal match on Day Thirteen of the 2014 US Open at the USTA Billie Jean King National Tennis Center on September 6, 2014.(Photo by Matthew Stockman/Getty Images)
2014 US Open - Day 13
Novak Djokovic of Serbia shakes hands with Kei Nishikori of Japan after their men's singles semifinal match on Day Thirteen of the 2014 US Open at the USTA Billie Jean King National Tennis Center on September 6, 2014. (Photo by Matthew Stockman/Getty Images)
