In the US Open, season's final grand slam, defending champions Serena Williams and Marin Cilic have entered into the third round today.In women's event world number one Serena, on course of a calendar slam, eased passed Kiki Bertens from Netherlands 7-6, 6-3 in the second round. She now faces Bethaine Sands of US in the third round. Two time champion Venus Williams of US, seeded players Agnieszka Radwanska of Poland and Canadian Eugenie Bouchard also entered third round today.In men's section, 9th seed and defending champion Marin Cilic recorded straight set victory in the second round over Russian Evgeny Donskoy 6-2, 6-3, 7-5. Spaniard Rafael Nadal the two time US Open champion and 10th seed Milos Ranoic of Canada were among others who entered the third round.In the men's doubles section a big upset was recorded as multiple Grand Slam winning Amercian pair of Bob and Mike Bryan crashed out in the first round to an unseeded pair. The top seeded pair lost to another American duo of Steve Johnson and Sam Querrey 6-7, 7-5, 3-6. Meanwhile, the Indo-Romanian pair of Rohan Bopanna and Florin Mergea entered the second round. They defeated American of Austin Krajicek and Nicholas Monroe 6-3, 6-4.The Wimbledon title holding mixed doubles pair of Leander Paes and Martina Hingis started their campaign on a winning note. Indo-Swiss duo beat Claire Liu and Taylor Harry Fritz of US 6-2, 6-2 in the first round.