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TORONTO, ON - JULY 30: Kei Nishikori of Japan prepares to serve against Stan Wawrinka of Switzerland during Day 6 of the Rogers Cup at the Aviva Centre on July 30, 2016 in Toronto, Ontario, Canada. (Photo by Vaughn Ridley/Getty Images)

TORONTO, ON - JULY 30:  Kei Nishikori of Japan prepares to serve against Stan Wawrinka of Switzerland during Day 6 of the Rogers Cup at the Aviva Centre on July 30, 2016 in Toronto, Ontario, Canada.  (Photo by Vaughn Ridley/Getty Images)

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TORONTO, ON - JULY 30: Stan Wawrinka of Switzerland hits a shot against Kei Nishikori of Japan during Day 6 of the Rogers Cup at the Aviva Centre on July 30, 2016 in Toronto, Ontario, Canada. (Photo by Vaughn Ridley/Getty Images)

TORONTO, ON - JULY 30:  Stan Wawrinka of Switzerland hits a shot against Kei Nishikori of Japan during Day 6 of the Rogers Cup at the Aviva Centre on July 30, 2016 in Toronto, Ontario, Canada.  (Photo by Vaughn Ridley/Getty Images)

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TORONTO, ON - JULY 30: Kei Nishikori of Japan hits a shot against Stan Wawrinka of Switzerland during Day 6 of the Rogers Cup at the Aviva Centre on July 30, 2016 in Toronto, Ontario, Canada. (Photo by Vaughn Ridley/Getty Images)

TORONTO, ON - JULY 30:  Kei Nishikori of Japan hits a shot against Stan Wawrinka of Switzerland during Day 6 of the Rogers Cup at the Aviva Centre on July 30, 2016 in Toronto, Ontario, Canada.  (Photo by Vaughn Ridley/Getty Images)

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TORONTO, ON - JULY 30: Stan Wawrinka of Switzerland hits a shot against Kei Nishikori of Japan during Day 6 of the Rogers Cup at the Aviva Centre on July 30, 2016 in Toronto, Ontario, Canada. (Photo by Vaughn Ridley/Getty Images)

TORONTO, ON - JULY 30:  Stan Wawrinka of Switzerland hits a shot against Kei Nishikori of Japan during Day 6 of the Rogers Cup at the Aviva Centre on July 30, 2016 in Toronto, Ontario, Canada.  (Photo by Vaughn Ridley/Getty Images)

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TORONTO, ON - JULY 30: Kei Nishikori of Japan reacts after losing a point against Stan Wawrinka of Switzerland during Day 6 of the Rogers Cup at the Aviva Centre on July 30, 2016 in Toronto, Ontario, Canada. (Photo by Vaughn Ridley/Getty Images)

TORONTO, ON - JULY 30:  Kei Nishikori of Japan reacts after losing a point against Stan Wawrinka of Switzerland during Day 6 of the Rogers Cup at the Aviva Centre on July 30, 2016 in Toronto, Ontario, Canada.  (Photo by Vaughn Ridley/Getty Images)