Six-time champion Novak Djokovic was stunned in straight sets by Hyeon Chung not long after Tennys Sandgren upset No 5 Dominic Thiem at the Australian Open.
The season-opening major often throws up unexpected results, but the back-to-back upsets Monday resulted in a longshot of a quarterfinal: Chung, the first Korean to reach the last eight at a Grand Slam, vs Sandgren, the American who had never won a Grand Slam match or beaten a top 10 player until last week.
The 58th-ranked Chung relentlessly attacked Djokovic - who is playing his first tournament since Wimbledon because of an injured right elbow - in the 7-6 (4), 7-5, 7-6 (3) fourth-round win.
"Yeah, today's victory for my country," said Chung, who ripped 47 winners, including a forehand on the slide and at full stretch that put him within two points of victory.
He credited the usually athletic Djokovic for the inspiration.
"When I'm young, I'm just trying to copy Novak because he's my idol," Chung said. "I can't believe this tonight. Dreams come true tonight."
Djokovic winced and grimaced throughout the match, particularly when stretching for backhands. He said he'd need to reassess the treatment for his elbow, but didn't want his injuries to detract from Chung's win
"Amazing. Amazing performance," said Djokovic, who was seeded 14th after his ranking slid in 2017 while he was off the tour. "Impressive. Whenever he was in trouble, he came up with some unbelievable shots. Just from the back of the court, you know, he was like a wall."
Chung was coming off a win over No 4-seeded Alexander Zverev.
Djokovic wasn't even sure until the last minute that he'd be able to play at Melbourne Park, and then had three tough matches against Donald Young, Gael Monfils and No 21 Albert Ramos-Vinolas.
"Once you're in the middle of the match, you're dealing with many things," he said. "I had similar situations in the past where I found myself struggling a little bit with some injuries during the match, then I managed to win.
"I felt the level of pain was not that high that I need to stop the match, even though it was obviously compromising my serve. That's life. I have to move on."
The 26-year-old Sandgren, who entered the season's opening major ranked 97th, missed a match point in the fourth set but held on for a 6-2, 4-6, 7-6 (4), 6-7 (7), 6-3 win over Thiem. It followed up his earlier victory over 2014 champion Stan Wawrinka.
"I don't know if this is a dream or not - all you guys are here, so maybe it's not," he said in an on-court TV interview after his 3-hour, 54-minute fourth-round win. "I'm not in my underwear, so maybe it's not a dream.
"I definitely had a real pinch-me moment."
Sandgren is only the second man in 20 years to reach the quarterfinals on his debut at Melbourne Park.
He converted half of his eight break-point chances, and fended off 10 of the 12 he faced against Thiem, and hit 63 winners against 38 unforced errors in the biggest win of his life.
"Trying to keep riding the wave," said Sandgren, who was named after his great-grandfather and who comes from Tennessee.
Angelique Kerber, the only Grand Slam singles winner remaining in the women's draw, was up earlier, and got a serious wakeup call.
For a while it appeared former Australian and US
Open champion Kerber's progression could unravel against No 88 Hsieh Su-wei, a former top-ranked doubles player with a double-handed grip on both sides, until she regained momentum for a 4-6, 7-5, 6-1 win. That earned Kerber a quarterfinal spot against U.S. Open finalist Madison Keys.
"Credit to her. She played an unbelievable match," Kerber , who is on a 13-match winning streak, said of her 32-year-old Taiwanese opponent.
"I was feeling I was running everywhere."
Keys returned to the quarterfinals here for the first time in three years with a 6-3, 6-2 win over No 8-seeded Caroline Garcia.
Top-seeded Simona Halep, who had to rally from triple match point down to advance through the third round, beat Naomi Osaka 6-3, 6-2.
Bopanna, Sharan lose
India's Rohan Bopanna and Divij Sharan lost their respective men's doubles third round matches in the Australian Open here on Monday.
Combining with Edouard Roger-Vasselin of France, Bopanna lost to Oliver Marach of Austria and Croatia's Mate Pavic 6-4 6-7 (5) 3-6 at the Melbourne Park.
The match lasted a little over two hours and saw the Indo-French duo convert one out of two break points, while their opponents converted three out of 12 break points.
Bopanna and Roger-Vasselin had two aces compared to their opponents' seven.
In an earlier match, the duo of Sharan and Rajeev Ram from the USA suffered a 6-3 6-7 (4) 4-6 defeat at the hands of lukasz Kubot of Poland and Brazil's world number one Marcelo Melo.
While Sharan and Ram converted two out of six break points, lukasz and his partner converted two out of four break points.
The third round match lasted two hours and 12 minutes.