Lee Zii Jia shocked two-time world champion Kento Momota to reach the semi-finals of the All England Open on Friday.
The Malaysian beat the world number one 21-16, 21-19 to end his Japanese opponent's tournament after a much-anticipated return to international action this week.
The pair went blow-for-blow up until the interval, taken at 11-8. Lee surged on from there, matching Momota's razor-sharp movement to win seven straight points and take the first game 21-16.
The 22-year-old drove home his advantage, stretching out to an 11-6 lead at the break in a white-knuckle second game in the empty arena in Birmingham.
Lee saw a net cord go his way to make it 20-19 and he went on to seal the match against the 2019 champion.
"I've never beaten him before, so this is a very special moment for me," said the Malaysian, who has long been a keen follower of the Japanese player.
"I did a lot of studying about Momota. Every time I played him, it seems like there's a big gap between us.
"I always discuss about what strategy I have to play against him, we worked a lot on that. Today is a big win for us."
The draw has opened up for Lee, who will face Mark Clajouw of the Netherlands in the semi-finals.
Momota, 26, who made a successful return to domestic badminton by winning the All-Japan Championship in December, was playing his first BWF world tour event since a January 2020 car crash in Malaysia, in which he suffered a fractured eye socket and his driver was killed.
He missed out on his planned comeback to the international tour in January after testing positive for Covid-19, which led to the Japan squad pulling out of three events in Thailand.
Denmark's second seed Viktor Axelsen beat Sitthikom Thammasin of Thailand 21-4, 21-15 to progress to the last four on Friday.
In the women's event, Japan's Nozomi Okuhara beat Thailand's Busanan Ongbamrungphan 18-21, 21-8, 21-16.
Indonesia's team were forced to withdraw from the tournament earlier this week after a passenger on their flight to Britain tested positive for the coronavirus.
With the All England Open not counting towards Olympic qualification, leading Asian badminton nations China, South Korea and Taiwan had opted not to travel because of Covid-19 restrictions.