Madrid - Top-ranked Victoria Azarenka and Maria Sharapova both beat Czech opponents to reach the third round of the Madrid Open on Tuesday.
The women's top two overcame dips in concentration to put away mistake-prone opponents.
Azarenka, the defending champion, held off Andrea Hlavackova's challenge to win 6-3, 7-6 (7/2) after Sharapova beat Klara Zakopalova 6-4, 6-3.
Azarenka has already won four titles this year, including the Australian Open, but showed less convincing form on the Magic Box's blue clay.
The Belorussian's backhand caught Hlavackova going the wrong way for a break point and 4-2 lead. She would save four break points in the ninth game before holding serve to take the opening set.
Hlavackova saved five break points to hold her serve and lead 2-1 in the second set, but was broken after double-faulting to trail 3-2.
Azarenka seemed to stutter toward the end as she double-faulted to be broken for Hlavackova to tie it up 5-5.
Azarenka saved set point with a forehand smash and took it to the tie-breaker where she moved out to 5-1 before clinching it when Hlavackova - who had needed treatment on her left thigh late in the second set - hit long.
Sharapova was more convincing in her second-round match, as Zakopalova's erratic serve opened her up to Sharapova's solid groundstrokes. Sharapova won the first of five breaks in the opening game and was in command after another break saw her lead 4-1.
Zakopalova came forward to break back in the next game but could get no closer as the pair held serve before Sharapova clinched the set with one of four aces.
Zakopalova was overpowered again on her opening serve but saved match point and broke back to get to 5-3 before her seventh double-fault clinched it for Sharapova.
In men's play, Marin Cilic of Croatia and Federico Delbonis of Argentina won their first-round matches.
Top-ranked Novak Djokovic makes his blue clay debut later Tuesday against Daniel Gimeno-Traver of Spain.
Results from the fourth day of the ATP and WTA Madrid Open on Tuesday (x denotes seeding):
Maria Sharapova (RUS x2) bt Klara Zakopalova (CZE) 6-4, 6-3
Victoria Azarenka (BLR x1) bt Andrea Hlavackova (CZE) 6-3, 7-6 (7/2)
Federico Delbonis (ARG) bt Albert Ramos (ESP) 6-3, 6-2
Radek Stepanek (CZE) bt Bernard Tomic (AUS) 6-2, 7-5
Marin Cilic (CRO) bt Albert Montanes (ESP) 6-3, 6-3
Andreas Seppi (ITA) bt Michael Llodra (FRA) 7-5, 6-4
Stanislas Wawrinka (SUI) bt Olivier Rochus (BEL) 6-4, 7-6 (7/3)
Alexandr Dolgopolov (UKR x16) bt Pablo Andujar (ESP) 7-6 (7/5), 6-4