Ly Hoang Nam upset Yu Cheng-Yu from Taiwan 6-2, 6-3 in the boys singles opener at the Asian Junior Tennis Championships in South Korea on Tuesday.
The loss came as a shock to the 17-year-old Taiwanese, who is ranked 88th in the world junior rankings and was seeded 5th at the event while the 15-year-old Vietnamese is ranked 283rd and entered the contest unseeded.
The upset win is another example of Nam's recent improvement. Early last month, he became the youngest ever to win Vietnam's national tennis championship.
In the second round of the November 6-11 competition in Korea, Nam will clash with the winner of the match between Duan Jiaqi of China and host player Jung Hyeon-il.
The other Vietnamese tennis talent at the contest, 17-year-old Nguyen Hoang Thien, ranked 138th, is the 14th seed. Thien came back from a set down to beat Korea's Sim Seongbin 3-6, 6-0, 6-1.