In season's final Grand Slam, the US Open Tennis, defending champions Serena Williams and Novak Djokovic have made their way into quarter finals. In the women's singles event, world number one and defending champion Serena Williams defeated fellow American Madison Keys 6-3, 6-3 in the round of 16 to set up a quarter final clash with her sibling Venus Williams tomorrow. Twice US Open winner, Venus stands in the way of Serena's quest for a rare calendar year grand slam. Serena is bidding to become just the fourth woman to win all four grand slams in the same year. The Williams sisters have met 26 times over their careers with Serena coming out on top 15-11.In the Men's Singles event, top-ranked Novak Djokovic cruised into the quarterfinals by beating Spain's Roberto Bautista Agut in the fourth round of the tournament a short while ago . Djokovic took 3 hour and 2 minutes to capture a 6-3, 4-6, 6-4, 6-3 victory over Bautista. Now, Djokovic will face Feliciano Lopez of Spain in the quarterfinals. Croatian Marin Cilic also made his way to the quarters after defeating 27th seed Jeremy Chardy from France 6-3, 2-6, 7-6, 6-1. Ninth seeded defending champion has set up his quarter final clash against 19th seed French Jo Wilfried Tsonga. In the Women's Doubles, the Indo-Swiss pair of Sania Mirza and Martina Hingis has sailed into quarter-final. Top seeded Martina and Sania defeated their 13th seeded rivals Michaella Krajicek of Netherlands and Barbora Strycova of Czech Republic in straight sets 6-3, 6-0 in the third round at the Louis Armstrong Stadium yesterday. The Indo-Swiss combination will now be pitted against ninth seeded pair of Chan sisters Yung-Jan and Hao-Ching of Taipei who rallied to overcome challenge of Romanian pair of Irina-Camelia Bequ and Raluca Olaru 5-7, 6-1, 7-6.