Top-seeded Juan Martin del Potro of Argentina used his dominating serve to beat Paul-Henri Mathieu of France 6-4, 6-4 in the Swiss Indoors quarterfinals on Friday.
Del Potro had 11 aces and never faced a break point against the 101st-ranked Mathieu.
In Saturday's semifinals, del Potro will play doubles specialist Edouard Roger-Vasselin of France, who beat Daniel Brands of Germany 6-3, 4-6, 6-3.
Roger Federer followed del Potro on court in a quarterfinal against eighth-seeded Grigor Dimitrov of Bulgaria.
The winner plays Vasek Pospisil of Canada in the semifinals. Pospisil beat Ivan Dodig of Croatia 7-6 (11), 6-4.