Olympic gallery: Djokovic out, Murray & Serena through

What. A. Day. Juan Martin del Potro sprung the upset of the Olympics with a straight sets win over Novak Djokovic, while Andy Murray and Serena Williams got their Gold medal defence off to the perfect start. These are the best photos from today at Rio 2016.

: Juan Martin del Potro downed Novak Djokovic 7-6(4) 7-6(2). Photo: Getty Images

: Novak Djokovic’s wait for an Olympic medal goes on. Photo: Getty Images

: Juan Martin del Potro downed Novak Djokovic 7-6(4) 7-6(2). Photo: Getty Images

: Djokovic and Del Potro had a long hug at the net. Photo: Getty Images

: Serena’s excitable hair. Photo: Getty Images

: Serena Williams kicked off her campaign with a 6-4 6-2 win over Daria Gavrilova. Photo: Getty Images

: Serena Williams kicked off her campaign with a 6-4 6-2 win over Daria Gavrilova. Photo: Getty Images

: Thomaz Bellucci and Andre Sa beat the Murray bothers 7-6(6) 7-6(14). Photo: Getty Images

: No.3 seed Garbine Muguruza downed Mitu 6-2 6-2. Photo: Getty Images

: No.3 seed Garbine Muguruza downed Mitu 6-2 6-2. Photo: Getty Images

: No.3 seed Garbine Muguruza downed Mitu 6-2 6-2. Photo: Getty Images

: Jo Konta won her first ever match at the Olympics, beating Vogt 6-3 6-1. Photo: Getty Images

: Andy Murray began his gold medal defence with a 6-3 6-2 win over Troicki. Photo: Getty Images

: Andy Murray began his gold medal defence with a 6-3 6-2 win over Troicki. Photo: Getty Images

: Angelique Kerber downedMariana Duque-Marino in straight sets. Photo: Getty Images

: What wrist problem? Rafa Nadal demolished Delbonis 6-2 6-1. Photo: Getty Images

: What wrist problem? Rafa Nadal demolished Delbonis 6-2 6-1. Photo: Getty Images

: Dustin Brown was forced to retire with a twisted ankle. Photo: Getty Images