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Washington, DC (Sports Network) - German Andrea Petkovic upended sixth-seeded compatriot Mona Barthel early on Wednesday before rain washed out the other three second-round matchups at the $235,000 Citi Open tennis event.

Petkovic needed just 48 minutes to dispose of Barthel 6-2, 6-2, on the hardcourts at FitzGerald Tennis Center.

Top-seeded Angelique Kerber of Germany was slated to take on American Melanie Oudin, but rain forced their matchup to be postponed until Thursday.

Two other second-round matches were pushed back until Thursday, as seventh- seeded Slovakian Magdalena Rybarikova will square off with Jana Cepelova, while Paula Ormaechea of Argentina will take on Russian Olga Puchkova.

The 2013 Citi Open champ will collect $40,000.