Kovinic moves into second round, Burger shocks McHale
Danka Kovinic qualified for the second round of the storm-affected Rio Open after securing victory over Sachia Vickery.
Play was delayed for over two hours on Monday due to the wet weather conditions in Rio de Janeiro, while contestants also had to deal with high levels of humidity in the hot weather.
Kovinic, the third seed, played through the tough conditions to secure a 6-3 5-7 6-4 win in just over two hours against her American opponent.
"It was so tough to play," Kovinic said after match. "It's very humid and hot here, and I came from Serbia, where it's very cold.
"For me, it was very hard to play. I felt like I didn't have energy, but somehow I found a way to finish the match.
"I really don't feel good right now."
Cindy Burger provided the upset of the day as the qualifier defeated fourth-seed Christina McHale 7-6 (7-5) 2-6 6-1.
McHale was not at her best as Burger - the world number 187 - saved 10 break points to knock off her opponent who sits 123 places above her in the rankings.
It was not the only shock of the day as unseeded Shelby Rogers defeated eighth-seed Andreea Mitu in straight-sets 6-2 6-2.
Francesca Schiavone also knocked out seventh-seed Tatjana Maria, while fifth-seed Polona Hercog advanced past Jennifer Brady 6-4 6-2.
In other results, Ana Bogdan defeated local wildcard Gabriela Ce 6-2 6-3, while Paraguay's Veronica Cepede Royg recovered from a set down to defeat Anna Tatishvili 6-7(4-7) 6-1 6-3.
Mariana Duque-Marino needed almost two and a half hours to beat Pauline Parmentier 7-5 6-7 (5-7) 6-3, Sorana Cirstea eased past Beatriz Haddad Maia 6-2 6-1, and Elista Kostova battled for a 7-5 7-5 win against fellow qualifier Maria Irigoyen.