Gurusaidutt, the defending men's champion, came through two rounds to reach the last four.
First he outclassed compatriot Mohit Kamat in pre-quarter finals and then the title holder stepped up his play when needed in the second game after trailing 4-7 to shut out Chinese Taipei rival Chia Hung Lu 21-12 21-18.
Thulasi, seeded fourth, could not counter the pace and power of her Chinese Taipei rival Chia Tsin Lee, the sixth seed, and went down in straight games.
Eighth seeded Sayali, who won the national crown last year at Srinagar, gave a good fight to Chinese Taipei's Yu Chieh Cheng before losing 10-21 25-23 21-19 in the pre-quarterfinals.
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For the major part of the one hour encounter between Sayali and Cheng, the Indian looked most likely to make the last eight grade. But it was Cheng's ability to raise the bar on crucial points that made the difference.
Also knocked out in the pre-quarters was the corresponding men's seed Anup Sridhar who was beaten 21-15 21-10 by Taipei's Chia Hung Lu.
Gurusaidutt will meet Varma tomorrow.
Last year's losing finalist and tournament top seed Febby Angguni of Indonesia sailed through to the last four with a 21-8 21-13 demolition of fifth seeded Indian rival Saili Rane in their quarterfinal match.