Fullerton (US): Young Indian shuttler Rounak Chouhan packed off world number six and top seed Chou Tien Chen of Chinese Taipei in straight games to create a big upset at the US Open here.World No. 80, Chouhan, who was part of India's bronze medal winning world junior campaign, defeated Chou 21-17 26-24 on Thursday to set up a quarterfinal clash against Misha Zilberman of Israel.The 18-year-old India kept the pressure on his more experienced opponent from the start and though Chou kept his nose ahead till 17-15, Chouhan won six straight points thereafter to pocket the opening game.Chou was the dominant player for most part of the second game as he commanded a 17-11 lead before Chouhan once again bagged six straight points to draw level.It was a neck-and-neck battle thereafter as Chouhan saved four game points before converting his second mach point to clinch victory in 49 minutes.Also advancing to the last-eight stage were world junior silver medallist Tanvi Sharma, Rakshitha Sree and Devika Sihag in the women's singles.Fifth seed Tanvi defeated Tung Ciou-Tong of Chinese Taipei 21-12, 21-19, Rakshitha got the better of Tung's compatriot Chen Su Yu 21-4, 21-19 while sixth seed Devika beat Tonrug Saeheng of Thailand 21-17, 21-19.The experienced Kidambi Srikanth then capped off a fruitful day for India with a 21-14, 21-13 win over Lee Zii Jia of Malaysia.