The Frenchman is set to face the winner of the second semi-final match between top seed Greek Stefanos Tsitsipas and No. 6 seed Italian Matteo Berrettini in the next round.
Halys secured victories against Richard Gasquet (7-6 (4), 7-6 (5)), Lukas Klein from Slovakia (6-3, 6-7 (7), 6-4), and Brazilian qualifier Gustavo Heide (6-1, 7-5) in the previous rounds of the Gstaad tournament.
Earlier in the week, No. 37 ranked Struff defeated Albert Ramos-Vinolas from Spain (7-6 (6), 7-6 (4)), Swiss wildcard Leandro Riedi (7-6 (6), 7-6 (1)), and No. 4 seed Tomas Martin Etcheverry from Argentina (7-5, 3-6, 6-3).
Gstaad ATP 250, other semi-final match (Roy Emerson Arena, clay, EUR 579,320):
- Stefanos Tsitsipas vs. Matteo Berrettini
