Stan Wawrinka set up a quarter-final clash with fellow home favourite Roger Federer at the Swiss Indoors Basel after seeing off Frances Tiafoe in three sets on Thursday.
Wawrinka, the seventh seed, triumphed 6-3 3-6 7-5 against American Tiafoe in a contest that lasted just over two and a half hours.
Top seed and defending champion Federer is looking to win the tournament for a 10th time.
Third-seeded Stefanos Tsitsipas battled back against qualifier Ricardas Berankis to win 6-7 (4) 6-2 6-4 and fourth seed Roberto Bautista-Agut beat Richard Gasquet 6-2 4-6 6-3.
But there were exits for the fifth seed, Fabio Fognini, and the sixth, David Goffin, as they lost to Filip Krajinovic and Reilly Opelka respectively.
Tsitsipas will now face Krajinovic for a semi-final place and Bautista-Agut takes on Opelka.
At the Erste Bank Open in Vienna, top seed Dominic Thiem moved into the quarter-finals as he came from behind to defeat Spain's Fernando Verdasco 3-6 6-3 6-2.
The Austrian will play another Spaniard in the last eight, Pablo Carreno Busta, who beat beat Mikhail Kukushkin of Kazakhstan 6-7 (3) 6-4 6-1.
Fourth seed Gael Monfils and fifth-seeded Diego Schwartzman also made it through, triumphing against wildcard Jannik Sinner and Sam Querrey.
Monfils' next opponent is Aljaz Bedene, who got past Gilles Simon, while Schwartzman plays second seed Karen Khachanov. Thursday's other match saw Andrey Rublev defeat Hyeon Chung.