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Den Bosch, The Netherlands (SportsNetwork.com) - Reigning champion Simona Halep highlighted Tuesday's winners at the Topshelf Open, a final grass-court Wimbledon tune-up.

The top-seeded Romanian star, fresh off her runner-up finish at the French Open two weeks ago, bested Belarusian qualifier Olga Govortsova 7-5, 6-2 in opening-round action at Autotron Rosmalen.

However, first-round upsets came when Kazakhstan's Yaroslava Shvedova took out second-seeded Australian Open runner-up Dominika Cibulkova, of Slovakia, 6-2, 3-6, 6-3 and American Vania King doused third-seeded Canadian Eugenie Bouchard 2-6, 6-3, 6-3. Bouchard was a semifinalist at this year's French and Aussie Opens.

In second-round play in The Netherlands, Slovak Magdalena Rybarikova took out fifth-seeded German Andrea Petkovic 6-4, 6-7 (4-7), 7-5 and seventh-seeded rising Spaniard Garbine Muguruza dismissed Austrian Yvonne Meusburger 6-4, 6-1. The French Open semifinalist Petkovic was the Den Bosch runner-up in 2010.

One other first-round match saw fourth-seeded Spaniard Carla Suarez Navarro tackle last week's Birmingham runner-up Barbora Zahlavova Strycova, of the Czech Republic, 6-4, 6-2.

On Wednesday, the world No. 3 Halep will face German Annika Beck in the round of 16. The Romanian stalwart beat Belgian Kirsten Flipkens in last year's Den Bosch finale.