German qualifier Jule Niemeier defeated defending champion Ons Jabeur 7-6 (4), 6-4 in the first round of the Berlin Open on Tuesday.

Jule Niemeier of Germany in action against Ons Jabeur of Tunisia in the first round on day 4 of the bett1open 2023 Berlin at LTTC Rot-Weiß eV on June 20, 2023 in Berlin, Germany (Robert Prange/Getty Images)

Niemeier, ranked 120th in the world, saved two set points at 5-3 down in the first set and then won the last four points of the tiebreak. Niemeier broke Jabeur in the first game of the second set and held her lead to win in 1 hour 35 minutes for the 23-year-old’s third win against a top 10 player.

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Coco Gauff defeated Czech player Katerina Siniakov 6-3, 6-4 for the American teenager’s 23rd win of the year.

Jule Niemeier at the party

Jule Niemeier of Germany in action against Ons Jabeur of Tunisia in the first round on day 4 of the bett1open 2023 Berlin at LTTC Rot-Weiß eV on June 20, 2023 in Berlin, Germany (Robert Prange/Getty Images)

The fourth-seeded Gauff next faces heavy hitter Ekaterina Alexandrova, who defeated fellow Russian Liudmila Samsonova 6-4, 6-3.

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Top seed Aryna Sabalenka advanced to the second round with a 6-3, 6-2 victory over veteran Vera Zvonareva in another all-Russian match.

Jule Niemeier preparing to hit a tennis ball

Jule Niemeier of Germany plays a forehand shot against Elise Mertens of Belgium during the women’s singles third round match on day six of the Mutua Madrid Open at La Caja Magica on April 29, 2023 in Madrid, Spain. (Jose Manuel Alvarez/Quality Sport Images/Getty Images)

Sabalenka converted three of her nine break points without facing any of Zvonareva, 38, a 2010 Wimbledon finalist.

Sabalenka now faces Veronika Kudermetova or Zheng Qinwen.

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Elina Avanesyan saved two match points and defeated sixth seed Daria Kasatkina with a 6-2, 3-6, 7-6(7) win to take on fellow Russian Anna Blinkova.