Stephens tops Osaka as both debut in WTA Finals

   In a matchup of the last two U.S. Open champions, No. 5 seed Sloane Stephens of Fort Lauderdale, Fla., beat No. 3 Naomi Osaka of Japan 7-5, 4-6, 6-1 today in a round-robin opener at the WTA Finals in Singapore.
   The 20-year-old Osaka, who defeated Serena Williams in a controversial final at Flushing Meadows in September, committed 46 unforced errors and fell to 0-2 against Stephens, a 25-year-old Fresno product.
   Both players debuted in the tournament, which features the top eight singles players and top eight doubles teams of the year.
   Also in the Red Group today, No. 8 seed Kiki Bertens of the Netherlands surprised No. 1 Angelique Kerber of Germany 1-6, 6-3, 6-4. Bertens replaced top-ranked Simona Halep, who withdrew from the tournament with a herniated disc.
   No. 6 seed Elina Svitolina of Ukraine and No. 7 Karolina Pliskova of the Czech Republic lead the White Group at 1-0. No. 2 Caroline Wozniacki, the defending champion, and No. 4 Petra Kvitova are 0-1.
   On Wednesday, Kerber is scheduled to face Osaka at 4:30 a.m. PDT, followed by Stephens versus Bertens. If Stephens wins in straight sets, she will qualify for the semifinals. If Stephens and Osaka win, Stephens will qualify as the group winner, and Kerber will be eliminated.