NEW HAVEN, Conn. - Defending champion and top-seeded Simona Halep was beaten in her opening match at the Connecticut Open, 6-2, 4-6, 6-3 by Slovakian Magdalena Rybarikova on Tuesday.
Rybarikova, ranked 68th in the world, broke the world's second-ranked player six times, including in the pivotal sixth game of the third set to go up 4-2. She then served out the win.
Earlier, American Alison Riske beat sixth-seeded Italian Flavia Pennetta 6-1, 7-6 (3).
The lone American left in the tournament earned five service breaks, four while cruising through the opening set.
Barbora Zahlavova Strycova of the Czech Republic also moved into the quarterfinals with a 7-5, 6-2 win over Caroline Garcia of France.
The final match of the night featured Wimbledon champion Petra Kvitova, the tournament's second seed, against Ekaterina Makarova of Russia.