SINGAPORE -- 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 in Singapore on Sunday.Kerber, who secured the top ranking last month, battled Cibulkova for 2 hours, 17 minutes before the Slovakian finally succumbed.It was a really good match from both of us, especially the first set, Kerber said. Its a good start to the tournament like this, where you knew you had to play your best to win.Earlier on Sunday, 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 Red Group action, Kerber and Halep stand at 1-0, while Keys and Cibulkova are at 0-1.On Tuesday, Kerber will play Halep, while Cibulkova and Keys, both making their WTA Finals debut, will play each other.Kerber posted 29 winners and 32 unforced errors to 36 winners and 34 unforced errors for Cibulkova.Cibulkova dropped serve in the opening game of the match, which initially allowed Kerber to establish a 4-2 lead in the first set.Kerber didnt hold on to the advantage, surrendering her own serve on a second double-fault in the eighth game.That sent the first set to a tiebreaker, where the German eventually prevailed.At the beginning I was too excited, but after a few games I started to play my game, Cibulkova said. It was a really tough one, really close, and in these kind of games its about the small details.Cibulkova dominated the second set, racing to 4-0 lead.In the third, Cibulkova was temporarily in charge with a 2-0 lead, but lost five of the next six games to end up on the losing side of the result.Its been a stellar season for Kerber, who won her first two Grand Slam titles at the Australian and US Opens, and also brought home the Olympic silver medal from Rio.Kerbers never journeyed beyond the round-robin stage of the WTA Finals in three previous appearances in 2012, 2013 and 2015.In the opening match, Keys played erratic tennis throughout the 69-minute contest, losing serve on four of 10 break points faced.I definitely think there were some nerves, Keys said. I think one of her strengths is making you feel like you have to go for more and take the risks. I think sometimes she makes me uncomfortable and I back away from playing my game.Keys held serve in the opening game of the match, but then saw Halep win the next five games for a 5-1 lead in the first set.Halep lost an initial 4-2 lead in the second set, but from 4-4 won the final two games.The Romanian reached the final here in 2014 and now holds a 5-1 head-to-head record against Keys.I think I played exactly what I had to play against her, Halep said. I was focused. Everything went as I wanted, so Im happy. Dan Marino Jersey . Thats about all he can do right now, so hes trying not to think about when he might be able to play again for the Los Angeles Lakers. Bob Griese Youth Jersey . -- Vincent Lecavalier got everything but the desired result in his return to Tampa Bay. http://www.dolphinsrookiestore.com/Dolphins-Bob-Griese-Jersey/ . 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KUALA LUMPUR, Malaysia -- Former badminton world champion Ratchanok Intanon has been cleared of a doping breach and will be allowed to compete at the Olympics next month.The Badminton World Federation issued a statement Monday saying it had lifted a provisional suspension on the No. 4-ranked Ratchanok, allowing Thailands Olympic medal hopeful to return to competition immediately.In the Thai capital Bangkok, Ratchanok broke down in tears as she spoke at a news conference held to announce the good news locally.It is my dream to compete at the Olympics. I thank all the team that helped me to go, she was quoted saying on the website of the Bangkok Post newspaper. I was always confident of my innocence. I didnt do anything wrong.Ratchanok, who in April who became a national heroine when she became the first Thai be ranked No.1 in womens singles, said she will resume training Tuesday, after the badminton federation had forced her to stop during the investigation.The BWFs doping hearing panel held an expedited hearing via video conference on Saturday for Ratchanok, who returned a positive sample during the Thomas and Uber Cup finals in China on May 15 for triamcinolone acetonidee, a class of steroid hormones known as glucocorticoids.ddddddddddddUse of the substance is prohibited during competition if administered orally, intravenously, intramuscularly or rectally, but the panel found that because administration of the substance was intra-tendinous -- directly into the tendon -- it did not require a therapeutic use exemption and was part of an ongoing medical treatment, so there was no violation committed.The BWF said the 21-year-old Ratchanoks medical background and records of treatment were submitted as part of the hearing.This evidence together with the testimony from the expert witness established to the satisfaction of the panel that the substance was administered on May 13, before the competition as part of on-going medical treatment of the athlete and that the route of administration of the substance was intra-tendinous, the statement said.The Olympic badminton tournament runs Aug. 11-20. The Post reported that the seven-member Thai badminton team along with staff will depart Bangkok for Rio de Janeiro on Aug 1. ' ' '