ESTORIL, Portugal - It did not take long for the upset bug to bite at the Estoril Open, as three of the four seeds in action went down on the first day of main draw play, including No.1 seed Agnes Szavay.

Twenty-year-old Anastasija Sevastova won the match's final five games after being down 3-1 in the third to upend Szavay, 36 63 63. The Latvian's victory should not be considered too much of a surprise, though, as she came up short but extended Szavay to three sets in their only previous clash in qualifying in Sydney earlier this year.

Up next for Sevastova is 39-year-old Kimiko Date Krumm, who was involved in Monday's wildest encounter, surviving Petra Martic, 67(4) 75 76(2), in 3 hours and 12 minutes, the seventh-longest match so far this year on the Sony Ericsson WTA Tour. Martic was two points from the match serving at 5-4 in the second set before Date Krumm rallied, and the Croatian herself rallied from 5-2 down in the third before Date Krumm eventually was victorious in the tie-break.

No.3 seed Aleksandra Wozniak and No.8 seed Sybille Bammer were both knocked out of the tournament in convincing fashion, as Julia Goerges beat Wozniak, 61 61, and Kirsten Flipkens topped Bammer, 61 63. The one seed who did advance was No.7 seed Peng Shuai, who was victorious in straight sets, as was her next opponent, Tatjana Malek.

Also Monday, Yvonne Meusburger, Arantxa Rus, Dia Evtimova and Nina Bratchikova secured main draw berths with wins in the final round of qualifying.

The highest seed left in the draw is among those in action Tuesday, as second-seeded Sorana Cirstea will try to avoid the upset trend when she takes on fellow Romanian Ioana Raluca Olaru.