Karolina Pliskova is into the semi-finals in Stuttgart, but world number one Simona Halep suffered an emphatic exit.
Martin Klizan made life difficult for Rafael Nadal at the Barcelona Open, but the 10-time champion showed his class on the clay once more.
An abdominal injury saw world number two Caroline Wozniacki withdraw from the Istanbul Cup and sent Pauline Parmentier into the semi-finals.
Martin Klizan became the first player to win five games in a set against Rafael Nadal on clay since last May, but he could not get the win.
World number one Simona Halep proved no match for Coco Vandeweghe in the quarter-finals of the WTA's Stuttgart Open.
Reigning Wimbledon champion Garbine Muguruza said a pre-existing back problem hastened her exit from the Stuttgart Open on Thursday.
He was slow to get going against Roberto Carballes Baena but Rafael Nadal was much happier with his defeat of Guillermo Garcia-Lopez.
The Stuttgart Open crowd were left displeased as Angelique Kerber and Garbine Muguruza both retired from their evening session matches.
She was forced to do it the hard way but Caroline Wozniacki overcame Sara Errani to advance to the Istanbul Cup quarter-finals.
The Rafael Nadal clay-court juggernaut rumbled on as Guillermo Garcia-Lopez proved no match for his compatriot at the Barcelona Open.