Australia’s Samantha Stosur has crashed out of the Prague Open in straight sets to world No.144 Beatriz Haddad Maia.

Stosur, the world No.19 and fourth seed, fell to the Brazilian qualifier 6-3 6-2 in 78 minutes.

The 33-year-old former US Open champion has twice been a runner-up on the Prague clay, losing to Israel’s Shahar Pe’er in 2006 and Lucie Safarova last year.

Stosur lost in the first round in Stuttgart last week following back-to-back round of 16 exits in Charleston and Miami.

Safarova was also out in the second round after withdrawing from the event due to illness, meaning Haddad Maia will now face Kristyna Pliskova in the quarter-finals.

Organisers said Safarova was ill before the tournament and her condition worsened after her 3-6 7-5 6-3 victory over Kristina Kucova on Tuesday.

Second seed and former No.1 Caroline Wozniacki was also a significant second-round casualty, losing a hard-fought battle 5-7 6-3 7-6 (5) to Latvia’s Jelena Ostapenko.

In other results on Wednesday third seed Barbora Strycova beat Lucie Hradecka 6-3 7-5 in an all-Czech clash and fellow local Katerina Siniakova defeated Russia’s Natalia Vikhlyantseva in three sets.

Italy’s Camila Giorgi came back from a set down to beat China’s Wang Qiang and Germany’s Mona Barthel did it easy against Oceane Dodin of France 6-3 6-1.