Stephens beats Bertens, improves to 2-0 in WTA Finals

   Sloane Stephens snapped Kiki Bertens' streak and improved to 2-0 with one round-robin match left in the WTA Finals.
   But Stephens, a 25-year-old Fresno product, still hasn't clinched a berth in the semifinals of the tournament, featuring the top eight singles players and top eight doubles teams of the year, in Singapore.
   Stephens, seeded fifth and ranked sixth, defeated Bertens, seeded eighth and ranked ninth, 7-6 (4), 2-6, 6-3 in a match that ended at almost 1 a.m. Thursday local time.
   Bertens, a 26-year-old Dutchwoman who replaced injured Simona Halep in the field, had beaten her last nine top-10 opponents. But Stephens needed to win in straight sets to advance.
   Earlier today, top-seeded Angelique Kerber of Germany outlasted third-seeded Naomi Osaka of Japan 6-4, 5-7, 6-4 in 2 hours, 30 minutes. On Friday in the Red Group, Stephens will face Kerber (1-1), and Bertens (1-1) will take on Osaka (0-2).
   On Thursday in the White Group, fourth-seeded Petra Kvitova (0-2) will play seventh seed and fellow Czech Karolina Pliskova (1-1) not before 1 a.m. PDT, followed by second seed and defending champion Caroline Wozniacki (1-1) of Denmark against sixth-seeded Elina Svitolina (2-0) of Ukraine.
   Kerber defeated Pliskova to win the 2015 Bank of the West Classic at Stanford. The tournament moved to San Jose this year under a new sponsor, Mubadala, after 21 years at Stanford.
   Osaka earned her first big win in the 2014 Bank of the West Classic. As a 16-year-old qualifier playing her first main-draw match on the WTA tour, Osaka ousted 2011 U.S. Open champion Samantha Stosur 4-6, 7-6 (7), 7-5 in the first round. Osaka saved a match point in the tiebreaker and overcame a 3-5 deficit in the third set.
   Osaka then fell to eighth-seeded Andrea Petkovic of Germany 6-2, 6-2. Petkovic reached a career-high No. 9 in 2011.