BERLIN -- Madison Keys started her German Open campaign with a 6-3, 6-4 win over Polish qualifier Magdalena Frech on Monday.
Keys, who is ranked 28th, hit three aces and saved four of the six break points she faced. She will next face the top-seeded Aryna Sabalenka in the second round of the Wimbledon warm-up tournament.
Keys, 26, is going for her third singles title on grass after wins in Eastbourne in 2014 and Birmingham two years later.
Another American, Amanda Anisimova, lost 6-3, 6-1 to Alize Cornet of France. Cornet next faces Canada's Bianca Andreescu.
Also, Ekaterina Alexandrova defeated Anna Kalinskaya 6-3, 6-2 in an all-Russian clash to set up a second-round meeting with second-seeded Elina Svitolina.
Belinda Bencic had to rally from a set down to get past German qualifier Jule Niemeier 4-6, 6-4, 7-5. Niemeier was playing her first professional grass-court tournament.