The US Open champion, the last of the four Grand Slams, needed two hours and 50 minutes to clear Osorio’s obstacle in the first match between the two players and the longest of two sets of the season.
“It has to be one of the most physical matches I’ve ever played,” the 19-year-old world number 10 said, adding, “I worked so hard to win it. I am so happy and proud of the way you fought back when it really mattered. That’s a lot of confidence after a match like this.”
And Radokano hit a quarter-final meeting with Russian Lyudmila Samsonova, 60, who ousted Australian Aja Tomljanovic by beating her 4-6, 6-3, 6-2.
China’s Wang Qiu also qualified by defeating Croatian Donna Vekic 4-6, 7-5, 6-1.
In men, Britain’s sixteenth Daniel Evans qualified for the quarter-finals, taking advantage of the withdrawal of the third American Taylor Fritz due to injury in the third set.
Evans will meet in the next round with Japanese Yoshihito Nishioka, who defeated Russia’s Karen Khachanov 7-6 (7-2), 7-6 (7-1).
Swede Michael Emer also reached the quarter-finals, defeating Finland’s Emil Rossofiori 6-3, 6-7 (3-7), 6-4.
Australian Nick Kyrgios, the Wimbledon runner-up, stopped playing with American Riley Opelka due to rain, while he was leading 7-6 (7-1) and 2-1.
For the same reason, the matches of Bulgarian Grigor Dimitrov with the American Sebastian Korda, the score 6-4, and the American Francis Tiafoe with the Dutchman Botic van de Zandschlub, the score 4-6, 6-2, were also stopped.