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Jack Sock of the US hits a return against Australia's Alex Bolt during their men's singles match on day two of the Australian Open tennis tournament in Melbourne on January 15, 2019. (Photo by Peter PARKS / AFP) / -- IMAGE RESTRICTED TO EDITORIAL USE - STRICTLY NO COMMERCIAL USE -- (Photo credit should read PETER PARKS/AFP/Getty Images)

Jack Sock of the US hits a return against Australia's Alex Bolt during their men's singles match on day two of the Australian Open tennis tournament in Melbourne on January 15, 2019. (Photo by Peter PARKS / AFP) / -- IMAGE RESTRICTED TO EDITORIAL USE - STRICTLY NO COMMERCIAL USE --        (Photo credit should read PETER PARKS/AFP/Getty Images)