Saina Nehwal suffered a shock defeat at the hands of Japanese Sayaka Sato in the second round of the Korean Super Series Badminton tournament in Seoul on Thursday.The world number four Indian lost 21-17 19-21 11-21 to Sayaka in 53 minutes in the women's singles. P Kashyap also became a second round casualty after losing 16-21 13-21 to third seed Peter Hoeg Gade of Denmark in 38 minutes in men's singles.In the mixed doubles category, Jwala Gutta and V Diju also tasted defeat at the hands of sixth seeded Chinese pair of Tao Jiaming and Qing Tian, losing in straight games 16-21 13-21. Saina, who missed on-court action for more than a month due to a ligament injury in her right knee, relied on her powerful smashes but Sayato played better at the nets to run away with the match.