Second-seeded Tomas Berdych eased into the ABN Amro World Tennis quarterfinals after Marcos Baghdatis retired with a left calf injury in the fourth game on Thursday.
Also, third-seeded Juan Martin del Potro fired nine aces to advance with a 6-4, 7-5 win over Karol Beck of Slovakia.
Baghdatis was injured in the opening games as Berdych raced to a 3-0 lead.
A physio strapped Baghdatis' calf and he returned to the court, but the Cypriot still hobbled and gave up a couple of points later.
In other second-round matches, fifth-seeded Richard Gasquet beat Alex Bogomolov Jr. 6-3, 6-2 and Andreas Seppi of Italy overcame Philipp Kohlschreiber of Germany 6-4, 6-2. Seventh-seeded Viktor Troicki beat Jesse Huta Gulang of the Netherlands 7-6 (2), 6-3 in just over two hours.
Top-seeded Roger Federer returns to action on Friday in a quarterfinal against Jarkko Nieminen of Finland.