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Croatia's Marin Cilic plays a backhand return to Ryan Harrison of the US during their men's singles third round match on day five of the Australian Open tennis tournament in Melbourne on January 19, 2018. / AFP PHOTO / PAUL CROCK / -- IMAGE RESTRICTED TO EDITORIAL USE - STRICTLY NO COMMERCIAL USE -- (Photo credit should read PAUL CROCK/AFP/Getty Images)

Croatia's Marin Cilic plays a backhand return to Ryan Harrison of the US during their men's singles third round match on day five of the Australian Open tennis tournament in Melbourne on January 19, 2018. / AFP PHOTO / PAUL CROCK / -- IMAGE RESTRICTED TO EDITORIAL USE - STRICTLY NO COMMERCIAL USE --        (Photo credit should read PAUL CROCK/AFP/Getty Images)