Melbourne: Chung Hyeon became the first South Korean man ever to reach the round of 16 at the Australian Open with a five-set upset win over fourth seed Alexander Zverev on Saturday.
The 58th-ranked Chung beat a top-five ranked opponent for the first time with his 5-7, 7-6 (7/3), 2-6, 6-3, 6-0 victory in 3hr 22min on Rod Laver Arena.
He will face either six-time champion Novak Djokovic or Spaniard Albert Ramos-Vinolas in Monday's fourth round.
Chung's feat also makes him only the third South Korean player -- man or woman -- to reach the round of 16 at a Grand Slam.
"It was really tough, he is a really good player and we know how to play each other," said the glasses-wearing 21-year-old, who trained in the heat of Thailand before coming to Melbourne.
"I played Novak two or three years ago, so if he wins tonight I just want to enjoy things on the court."
It was another disappointing exit from a Grand Slam for the highly-ranked Zverev, whose game fell apart in the final set and was issued with a warning for smashing his racquet in frustration after a service break.
While he won five titles and was one of just four players to beat Roger Federer last year, he has yet to get beyond the fourth round at a Grand Slam.
To rub salt in the wounds, it was a Zverev family double for Chung who eliminated older brother Mischa in the first round of the tournament.
Zverev got off to a quick start to hold three set points with a backhand cross court and took the opening set in 44 minutes when Chung netted a forehand.
But Chung, who defeated Russian Andrey Rublev to claim his first title at the Next Gen ATP finals in Milan last year, levelled the set scores with a tiebreaker win after holding three set points when the German netted a forehand.
Zverev hit the front with a break in the third game on the way to taking the third set but Chung would not go away.
The South Korean took the match into a fifth set with a booming ace and Zverev handed over a break in the opening game of the deciding set with a double fault on triple break point.
Zverev was given a racquet abuse warning by the chair umpire after slamming his racquet into the court in frustration and suffering a second service break to trail 3-0 as his game fell away.