Muguruza, Keys advance in Linz
Garbine Muguruza and Madison Keys advanced to the second round of the Generali Ladies Linz with straight-sets wins, while Carla Suarez Navarro secured a quarter-final spot.
Top seed Muguruza will guarantee her place at the WTA Finals in Singapore if she takes the title on her first appearance in the Austrian tournament, her campaign getting off to a strong start with a 6-4 6-4 victory over Cagla Buyukakcay.
The French Open champion required four attempts to wrap up the first set, but a single break at the start of the second proved enough to set up a second-round clash with former world number two Monica Niculescu.
"It was a tough first round. I think we both played well, so it was a battle out there, and a great feeling to start the tournament with a win like this," said Muguruza.
"I've never played against her [Niculescu], or even practiced together, so it'll be interesting. I think we have opposite styles, so I think it's going to be a fun match."
Wildcard and third seed Keys will also be hoping for a positive result to secure a spot in Singapore, and she had to fight from 4-2 down in the second set to overcome Camila Giorgi 6-3 6-4.
Suarez Navarro comfortably saw off fellow Spaniard Sara Sorribes Tormo 6-4 6-1 to set up a last-eight match against Denisa Allertova, who defeated Anett Kontaveit 6-3 6-4.
Dominika Cibulkova cruised past Belinda Bencic 6-1 6-2, while French qualifier Oceane Dodin eliminated Sorana Cirstea 6-2 6-4 and Mandy Minella's retirement handed Kirsten Flipkens passage to the second round, where defending champion Anastasia Pavlyuchenkova awaits.