BASEL, SWITZERLAND - OCTOBER 29: Marin Cilic of Croatia in action during the Swiss Indoors ATP 500 tennis tournament semi-final match against Mischa Zverev of Germany at St Jakobshalle on October 29, 2016 in Basel, Switzerland. (Photo by Harold Cunningham/Getty Images)
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Getty Images Sport Harold Cunningham

BASEL, SWITZERLAND - OCTOBER 29: Marin Cilic of Croatia in action during the Swiss Indoors ATP 500 tennis tournament semi-final match against Mischa Zverev of Germany at St Jakobshalle on October 29, 2016 in Basel, Switzerland. (Photo by Harold Cunningham/Getty Images)
Getty Images

Getty Images Sport Harold Cunningham

BASEL, SWITZERLAND - OCTOBER 29: Marin Cilic of Croatia in action during the Swiss Indoors ATP 500 tennis tournament semi-final match against Mischa Zverev of Germany at St Jakobshalle on October 29, 2016 in Basel, Switzerland. (Photo by Harold Cunningham/Getty Images)
Getty Images

Getty Images Sport Harold Cunningham