LONDON, ENGLAND - NOVEMBER 17: Alexander Zverev of Germany reacts against Roger Federer of Switzerland during Day Seven of the Nitto ATP Finals at The O2 Arena on November 17, 2018 in London, England. (Photo by Fred Lee/Getty Images)
LONDON, ENGLAND - NOVEMBER 17: Alexander Zverev of Germany reacts against Roger Federer of Switzerland during Day Seven of the Nitto ATP Finals at The O2 Arena on November 17, 2018 in London, England. (Photo by Fred Lee/Getty Images)