Belinda Bencic beat fifth-seeded Karolina Pliskova 6-3, 4-6, 6-3 to reach the semis, ensuring her return to the top 20 in the rankings.
''I wouldn't believe I win today again,'' Bencic said. ''I'm not going to the court with any expectation. I'm just trying to play. This is the mentality I have, and this is the mentality I'm going to keep having.''
Bencic's victory set up a semifinal against No. 8 seed Angelique Kerber, who beat error-prone Venus Williams 7-6 (3), 6-3 in a match-up of 30-somethings.
Williams led 4-2 in the first set before Kerber won three straight games to go up 5-4.