Gaston, albeit at only 1.73 metres, is the last French man standing out of the 18 that started in the main draw at this year's tournament, wrapped up the contest with a bagel in the deciding set agains the three-time Grand Slam champion.
The Swiss, whose only loss to a Frenchman in 10 previous matches at Roland Garros was against Jo-Wilfried Tsonga in 2012, ran out of steam as the 20-year-old, ranked 239th, romped to victory in front of the vociferous Court Suzanne Lenglen fans.
"I tried to play my game, I entered the court to win even if I didn't think I could win," Gaston said in his court-side interview.
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Gaston, who broke Wawrinka eight times, will next face Austrian third seed and U.S. Open champion Dominic Thiem, the runner-up at Roland Garros in the last two years.
"It's going to be a crazy experience (against Thiem). I'm going to give everything, just like today and we'll see the result. I will have nothing to lose," he said. (Reporting by Sudipto Ganguly; editing by Ken Ferris)
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