Lucky loser Keys quickly abandoned her books in the players' lounge as she made a dash for centre court after being handed a place in the main draw following the late withdrawal of Tamira Paszek through injury.
With no time to dwell on what was happening, the 18-year-old from Illinois quickly dismantled fifth-ranked Li's game to secure a shock 6-3 6-2 win for her first career victory against a top-10 opponent.
"I had practiced really early this morning and then kind of sat around waiting all day," Keys said.
"And then like 10 minutes before the match I got a text message saying 'yeah you're going on so go get ready'."
A product of the Evert Tennis Academy in Florida, Keys said not having time to think about the match worked in her favour.
"Just having no idea and then all of a sudden I was excited and the adrenalin was going and all that," the world number 63 said.
"I just kind of started playing and felt really good and I was able to win.
"Not overthinking it all day and sitting around and kind of worrying about it I think really helped."
Her opponent in the second round will be Spanish wildcard Anabel Medina Garrigues.
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