France's Kristina Mladenovic, seeded seventh, lost in the first round of the St. Petersburg Ladies Trophy on Wednesday after a two-hour battle with Laura Siegemund of Germany.

World No. 87 Siegemund, who is only in the main draw as a replacement for an injured player, took the initiative in the second set against the 30th-ranked Mladenovic to win 1-6, 7-5, 6-1.

Siegemund now faces either Belgium's Kirsten Flipkens or promising young Russian Darya Kasatkina in the second round.

Later Wednesday, world No. 16 Roberta Vinci of Italy, seeded second in St. Petersburg, faces Belgium's Yanina Wickmayer in the second round.

Ana Ivanovic of Serbia, seeded fourth, takes on Russia's Margarita Gasparyan.