Minh, the tournament's No 2 seed, was defeated by Chinese player Xue Song 15-21 and 10-21 in 38 minutes.
Xue, who is not even in the top 200 of the world rankings, dominated play from the beginning of the match. He gave Minh no chance to resist his strong volleys and smashes. The second set was a nightmare for Minh. Although he switched to a highly defensive style of play, he failed to turn the tables.
Xue has become a giant killer in Sydney as on April 4 he downed Indonesian legend Taufik Hydayat, the No 6 seed.
He will next play the winner of the match between Alamsyah Yunus, No 12, of Indonesia and Lee Dong-keun from the Republic of Korea in the semi finals on April 6.
The unexpected loss will hit Minh hard, who is No 9 in the world rankings. Minh is sure to fall in the rankings as he could not defend his position at the last year's tournament. Last year, he entered the final match before losing to Chinese player Jin Chen 11-21 and 1 2-21.
The Open will conclude on April 7 while the Badminton World Federation's new rankings will be released early next week.