Kerber struggles in Finals opener

Top-seeded Angelique Kerber struggled to defeat seventh-seeded Dominika Cibulkova 7-6 (5), 2-6, 6-3 on the opening day of the WTA Finals at Singapore.

Kerber, who secured the top ranking last month, battled Cibulkova for two hours, 17 minutes.

Third-seeded Simona Halep won the first match of the round-robin portion of the tournament by taking a 6-2, 6-4 decision over sixth-seeded American Madison Keys. In other news: • Juan Martin del Potro of Argentina won the Stockholm Open to end a 33-month title drought, beating sixthseeded Jack Sock of the United States 7-5, 6-1.

• Pablo Carreno Busta of Spain came back from a set down to beat Italy’s Fabio Fognini 4-6, 6-3, 6-2 and win the Kremlin Cup at Moscow.

• Third-seeded Richard Gasquet of France beat unseeded Argentine Diego Schwartzman 7-6 (4), 6-1 to win the European Open final at Antwerp, Belgium.