BASTAD, Sweden (AP) -- Top-ranked Caroline Wozniacki has retired from her second-round match at the Swedish Open against local favorite Sofia Arvidsson because of a shoulder injury.
The Dane won the first set 6-2 Wednesday and lost the opening game of the second when she was forced to quit.
Second-ranked Flavia Pennetta also advanced after defeating Angelique Kerber of Germany 6-2, 6-3. The Italian will face seventh-ranked Barbora Zahlavova Strycova of the Czech Republic.
Eighth-seeded Polona Hercog of Slovenia rallied to beat defending champion Aravane Rezai of France 3-6, 6-4, 7-6 (4), and fourth-seeded Lourdes Dominguez Lino downed Arantxa Parra Santonja 7-5, 6-1 in an all-Spanish match.