Venus Williams was given a fright by Garbine Muguruza before progressing to the quarter-finals of the Brazil Tennis Cup.
The top seed, playing in her first tournament since the Australian Open, overcame a mid-match wobble to beat Muguruza 6-4 2-6 7-5.
Williams, who needed four match points to end the Spaniard's challenge, will now face fifth seed Magdalena Rybarikova.
The Slovakian was also taken the distance before she beat Beatriz Garcia Vidagany 6-4 3-6 6-4.
There was an upset as South African fourth seed Chanelle Scheepers was beaten 6-1 6-2 by Timea Babos.
The Hungarian's reward is a quarter-final tie against Monica Niculescu, whose own victory was even more comprehensive, 6-1 6-1 over Tereza Mrdeza.
Seventh seed Kristina Mladenovic also had a simple outing as she overcame Tatjana Malek 6-2 6-1.
Melinda Czink beat Beatriz Haddad Maia and Olga Puchkova saw off Caroline Garcia, both coming from behind to win in three sets.
