Eighth seed Sameer, who had reached the finals at Hong Kong Super Series last year, rode on his powerful smashes to dish out a tricky game and stun second seed and world number 14 Vittinghus, who is coming back after undergoing a surgery due to apendicitis, 21-15 21-13 in a 35-minute clash.
It was 15th seed Harsheel, 20, who started the proceeding when he dumped 12th seed Denmark's Holst 21-16 17-21 21-11 in a thrilling contest at the Babu Banarasi Das Indoor Stadium.
Olympic silver medallist P V Sindhu expectedly brushed aside Vaidehi Choudhari 21-15 21-11 in another lop-sided contest, while defending champion Kidambi Srikanth boosted his confidence with another 21-12 21-17 win over Malaysia's seventh seed Zulfadli Zulkiffli.
While China Open champion Sindhu, world ranked sixth, will face Indonesia's fourth seed Fitriani Fitriani, who edged out Polish Open winner Rituparna Das 21-17 13-21 23-21 in a hard-fought battle. Srikanth will meet compatriot B Sai Praneeth, seeded ninth and who prevailed 21-19 12-21 21-10 over compatriot Sourabh Varma, seeded 11th, in another match.
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At the first game, he broke off at 4-4 to quickly move to a 11-6 lead at the break after pushing the shuttle at the back of the court. His quick reflexes and angled returns helped him to gather points at will as he eventually sealed the opening game when Vittinghus found the net.
Harsheel, who has been training at the Uday Pawar academy for last 14 years, however, had to dig deep in his reservoir to dismantle the World No 47 Holst. The Mumbaikar walked away with the opening again without being troubled much after opening up a 7-3 lead early on.
In the second game, Harsheel had a 10-6 lead but he blew it as Holst made a comeback, despite a late fight by the Indian. However, the strapping left-handed shuttler changed his gears in the decider to zoom past his opponent as he lead 10-1 at one stage and didn't give any chance to Holst to make any comeback.