American teenager Madison Keys was immersed in her algebra homework when she got the message that she was due on court in 10 minutes to play fifth seed and former French Open champion Li Na at the Madrid Open.
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.