Chung Hyeon took up tennis after a doctor recommended that peering at a green court would help his weak eyesight, and the bespectacled South Korean has never looked back.
He is now in the quarter-finals of the Australian Open after the biggest win of his career against 12-time Grand Slam winner Novak Djokovic.
Nicknamed "The Professor" due to his trademark thick white-rimmed glasses, the 21-year-old is in electric form, having dumped fourth seed Alexander Zverev out in the third round.
It has been a gradual build-up for Chung.
He won the 2015 ATP Most Improved Player award, and signalled his intentions with a run to the semis in Munich last year before his big breakthrough at the Next Gen ATP finals in Milan in November.
Employing his trademark defensive speed and scything forehand, he upset top-seeded Russian Andrey Rublev for his first title and has carried the form into Melbourne after an off-season training in Bangkok.
He models his game on Djokovic -- his idol -- and did his best impersonation of the Serb to knock him out sensationally on Monday.
"I'm trying to copy Novak because he`s my idol," he said, adding that he was keen to get a selfie with him after managing to get one with Rafael Nadal, "I have picture taken with Rafa last year. So one by one," he added.
Chung is the first player -- man or woman -- from South Korea to reach the last eight of a Grand Slam as his meteoric rise gathers pace.
In his homeland, the mass-circulation Chosun Ilbo newspaper said the world had been "caught by surprise", although the response was muted with tennis not massively popular.
Former South Korean president Lee Myung-Bak though was enthused, praising Chung's "strong mentality and technique" in a Facebook post.Chung started playing tennis aged six, encouraged by his father Seok-Jin -- a tennis coach. His brother Hong is also a semi-professional player.
Struggling with poor eyesight from a young age, he would blink constantly and an optometrist diagnosed him with myopia and astigmatism, suggesting Chung should play tennis as seeing the green court would help.
"I always play with the glasses," he said this week. "Without the glasses, I can see guys, but I can't play the same tennis."
Chung has said he has no plans to get surgery to fix the problem because he would "feel bare" without his spectacles.
It has clearly not been a hindrance as he zeroes in on a clash against another surprise packet, American Tennys Sandgren, on Wednesday for a place in the semi-finals.
"I'm just trying to focus on the moment," he said. "I have to be ready."
Chung trained at the IMG Academy in Florida for two years from the age of 13, and also completed a month of military training in South Korea.
He shyly confided this week that he doesn't have a girlfriend, and that he likes to eat Chinese food before a match -- Korean is too heavy apparently.
And in an interview with a South Korean news agency in November, he revealed his favourite activity.
"What I like to do most is just rolling on my bed. I can do that for days," said the quirky Korean, whose exploits are fast earning him a reputation as an emerging star.