Kerber, Muguruza through in Monterrey

Angelique Kerber and Garbine Muguruza booked their spots in the Monterrey Open second round on Tuesday.

Kerber, the top seed and two-time runner-up, overcame qualifier Kristina Kucova 7-6 (7-4) 6-2 on the hard-courts in Mexico.

The German's two final defeats at the WTA International event have come to four-time champion Anastasia Pavlyuchenkova.

Pavlyuchenkova started her bid for a fifth crown with a 6-0 6-3 thrashing of Russian compatriot Anna Blinkova.

.@AngeliqueKerber slides into the @Abierto_GNP second round! Takes a 7-6(4), 6-2 win over Kucova! pic.twitter.com/DW6ij1Z30O

— WTA (@WTA) April 3, 2019

Meanwhile, defending champion Muguruza was tested before getting past Romanian Elena-Gabriela Ruse 6-4 7-6 (7-4).

Also in Monterrey, two-time grand slam champion Victoria Azarenka eased through her opener against qualifier Miyu Kato 6-4 6-2.

Kristina Mladenovic battled through, while the only seed to fall was Alison Riske, who was beaten by Sachia Vickery 7-6 (8-6) 6-1.

At the Charleston Open, former champions Sloane Stephens and Kiki Bertens reached the third round.

Stephens, the 2016 winner struggling for form so far this year, battled past Sara Sorribes Tormo 7-6 (7-4) 7-6 (7-4).

.@SloaneStephens displayed some incredible hands at the net in her opener at the @VolvoCarOpen! #ShotOfTheDay pic.twitter.com/s2I7CmCjH5

— WTA (@WTA) April 3, 2019

Bertens, the defending champion and second seed, had fewer problems, crushing qualifier Martina Trevisan 6-2 6-1.

In first-round matches, the likes of Kaia Kanepi, Danielle Collins and Andrea Petkovic won through.