World number six Karolina Pliskova held her nerve to secure a hard-fought 6-2 1-6 7-5 victory over Victoria Azarenka in round two of the Madrid Open.
Pliskova, 26, eased to the first set only for fellow former world number one Azarenka, 28, to respond by winning five straight games to take the second.
The Belarusian, playing her first clay tournament in two years, hit back from 3-0 down to level the deciding set.
But Pliskova held a tense 11th game before breaking serve to win the match.
The Czech, who won the Stuttgart Open last week, will face Sloane Stephens in round three after the US Open champion beat Australia's Samantha Stosur 6-1 6-3.