Top seed Teliana Pereira suffered a shock first-round exit at the WTA Rio Open, but Johanna Larsson comfortably made it into round two.
Home favourite Pereira was the favourite in Tuesday's contest against Petra Martic, a player 119 places below her in the rankings.
But it was Croatia's Martic that booked a spot in round two courtesy of a 6-3 7-5 victory in the Brazilian capital. The world number 162 applied constant pressure on Pereira's serve and took three of nine break-point chances she created.
Next up for Martic is Marina Erakovic, who needed three sets to dispatch of Maria-Teresa Torro-Flor in a 7-6 (10-8) 6-7 (5-7) 6-2 victory.
While Pereira fell at the first hurdle, Larsson - seeded second - was a 7-5 6-4 victor over Lourdes Dominguez Lino, and next faces Paula Goncalves after the qualifier beat Julia Glushko 6-3 6-1.
There was double Spanish delight as sixth seed Lara Arruabarrena saw off Rebecca Peterson 6-0 6-3 and Silvia Soler-Espinosa defeated Romina Oprandi 6-1 6-2.