Fifth seed Sara Errani became the first major casualty of this year's Wimbledon as she was upset by teenager Monica Puig.
Italian Errani, who reached the semi-finals of the recent French Open before losing to eventual winner Serena Williams, went down 6-3 6-2 to her Puerto Rican opponent.
Puig did have the form for an upset however, having sent Nadia Petrova to a first-round defeat in Paris.
And the trick was repeated again today as 19-year-old Puig, ranked 60 places below Errani in the world at 65th, overcame some late jitters to cash in a seventh match point before breaking down in tears.
She hit a total of 35 winners against her stunned opponent, who was perhaps still reeling from taking just one game from Williams at Roland Garros.
Despite her top-level success consisting largely of the victory over Petrova and now this one, Puig has become a sporting national hero in Puerto Rico.
Even though she moved to Miami as a child, she retains strong links with her home town of Hato Rey, and is following in the footsteps of the well-respected Gigi Fernandez.
A former Wimbledon semi-finalist, Olympic winner and multiple grand slam doubles champion, Fernandez put Puerto Rico on the map as a tennis nation and Puig is keen to make a similar impression.
Today's game was streamed live on two television channels at home, and she said: "I moved to America at a relatively early age but I never forget where I am from and return there every single summer.
"My grandparents still live there and I am very proud to be one of the only tennis players from Puerto Rico.
"Everyone will have been watching. It was live on TV and I am a bit of a hero there and it's great that tennis is becoming bigger.
"I am obviously trying to go down the way Gigi Fernandez did, but more as a singles player."