Nikola Mektic Pictures
LONDON, ENGLAND - NOVEMBER 13: Nikola Mektic of Croatia and Alexander Peya of Austria return the ball during their doubles round robin match against Raven Klaasen of South Africa and Michael Venus of New Zealand during Day Three of the Nitto ATP World Tour Finals at The O2 Arena on November 13, 2018 in London, England. (Photo by Julian Finney/Getty Images)