Rio de Janeiro - Japan's Taro Daniel caused the biggest shock on the first day of the Olympics tennis tournament on Saturday when the world number 117 stunned US 14th seed Jack Sock.
Daniel, born in New York to an American father and Japanese mother, but who lives in the Spanish city of Valencia, eased to a 6-4, 6-4 win.
The 23-year-old, who next faces Britain's Kyle Edmund, said the win was one of the best of his career that justified his decision to play the Olympics rather than chase ranking points at second-tier events in Europe.
"I'm a young player. I wanted to prioritise things that are going to be positive to my career experience," said Daniel.
"I can't really rush with the points. It makes sense for the older guys, I guess, to skip this and save their energy for the Grand Slams.
"I could have just stayed in Europe, trying to get more points. But I am getting some really unbelievable experience and I feel like I am part of something much bigger."