Julia Goerges of Germany posted a first- round upset win over Wimbledon runner-up Agnieszka Radwanska at the Olympics on Sunday.
Goerges outlasted Radwanska, the No. 2 seed, by a 7-5, 6-7 (5-7), 6-4 margin at the All England Club.
Rain forced the match to be played under the retractable roof on Centre Court. It was the first time Olympic tennis has been played indoors in the modern era.
Meanwhile, third-seeded Russian Maria Sharapova handled Shahar Peer of Israel 6-2, 6-0 in 65 minutes on Centre Court.
Sharapova won the French Open last month to complete the career Grand Slam. She carried the Russian flag in the opening ceremony.
A shoulder injury forced Sharapova to miss the 2008 Olympics.
Only three other first-round matches were completed Sunday due to the inclement weather.
Kazakhstan's Yaroslava Shvedova posted a 6-4, 6-2 victory over Simona Halep of Romania, Hungarian Timea Babos bested Shvedova's countrywoman Galina Voskoboeva by the same score and Anna Tatishvili of Georgia advanced with a 6-2, 6-0 rout of Liechtenstein's Stephanie Vogt.