The 20-year-old twice fought back from a break down in the final set before he saved four match points at 5/6, 7/8, 9/10, and 10/11 in a mammoth tie-break to advance in two hours and 20 minutes. He has now claimed 17 clay-court wins at all levels this season, having reached ATP Challenger Tour finals at the Concord Iasi Open and the Roma Garden Open I.
“I am very happy to be in my first [ATP Tour] semi-final,” Gaston said. “It was a great fight. It was a really long match. I always tried to play my game, and it is a good win for me. I hope I can continue like that.”
The World No. 155, who was competing in his first tour-level quarter-final on Friday, becomes the youngest Gstaad semi-finalist since 2006, when a then 17-year-old Marin Cilic enjoyed a run to the last four.