STUTTGART, GERMANY - APRIL 24: Antonia Lottner of Germany plays a forehand to Marta Kostyuk of Ukraine on day 2 of the Porsche Tennis Grand Prix at Porsche-Arena on April 24, 2018 in Stuttgart, Germany. (Photo by Alex Grimm/Getty Images)
STUTTGART, GERMANY - APRIL 24: Antonia Lottner of Germany plays a forehand to Marta Kostyuk of Ukraine on day 2 of the Porsche Tennis Grand Prix at Porsche-Arena on April 24, 2018 in Stuttgart, Germany. (Photo by Alex Grimm/Getty Images)