Rafael Nadal limped off the court after quitting in pain early in the fifth set on Tuesday to send Marin Cilic into the semi-finals of the Australian Open 3-6, 6-3, 6-7 (5-7), 6-2, 2-0.
The Spanish top seed, who had been treated on his upper right in the fourth set, pulled the plug after almost four hours of intense battle with the sixth seed and 2017 Wimbledon finalist.
Nadal came to Melbourne with a huge question mark hanging over his right knee as he started his season late.
The 31-year-old failed to finish a match for only the third time in almost nine years, with one of his pullouts coming in Melbourne, 2010, in a quarter-final against Andy Murray.
Cilic now faces a semi with unfancied Briton Kyle Edmund, who stunned third seed Grigor Dimitrov 6-4, 3-6, 6-3, 6-4.
Nadal was strugling to walk normally as he left the court, after quitting as he lost the second game of the fifth set despite saving five break points before being caught by a Cilic pass.
“It was an unbelievable performance from both of us,” the Croatian said. “It was uncomfortable for Rafa, but he’s a competitor who always gives his best.
“It was sad to see him finish like this. I had to continue with my own game and not look too much across the net.”
Cilic last beat Nadal nearly a decade ago, in Beijing, 2009, losing their next five.
This Melbourne edition will be the first since 2007 when at least two of the big four – Roger Federer, Nadal, Novak Djokovic and Andy Murray – were not a part of the semi-finals.
Edmund’s elimination of Dimitrov came with the Brit carrying the weight of his nation after Murray was forced to miss the major following knee surgery.
Number 49 Edmund is only the sixth British man to reach a grand slam semi since Open tennis began in 1968. One of that number, Tim Henman, was in the stands watching the upset.
“You don’t think about records when you are playing,” Edmund said. “But it’s something to be proud of.
“Right now, I just want to keep going. I’m feeling very happy, now I’m trying to enjoy every moment.”
Edmund surprised Dimitrov by winning the opening set and did not falter when he then lost the second before gunning his jets over the next two sets to earn the win.
“I had a dip in the second set, but I came back late in the third,” the winner said. “I held my nerve in the fourth and broke at the end (5-4 before serving out the victory a game later).”
Edmund won in two hours 49 minutes, striking 46 winners and sending over 13 aces.
“Kyle deserves to win, simple as that,” Dimitrov said. “He’s been working so hard the past months. I’ve seen that.
“I take full responsibility of my match today. There’s no point for me to say what I did wrong: it’s all about him right now. He’s the winner.
“I’m disappointed, it hurts, and so it should.”
In the women’s draw, Belgium’s Elise Mertens continued her golden tournament debut defeating injured fourth seed Elina Svitolina 6-4, 6-0 to earn the first of the semi-final spots.
The 22-year-old, who trains at the academy of former Belgian great Kim Clijsters, was hoping that her mentor might have been up in the early hours back home, watching the quarter-final showdown.
“I’m trying to follow in your footsteps, Kim,” Mertens said.
Svitolina, from Ukraine, was tipped as a title favourite and had been in the running for a shot at the WTA number one title before she fell victim to Mertens.
She later revealed that she has been dealing with a left hip injury throughout the event, managing to play only with the help of painkillers.
“I’m without words, I don’t know what to say,” the 39th-ranked Mertens said. “I gave all I had today, even if was a little stressy at the end.
“It’s amazing, not expected, especially today. I was in the zone, it was a really great match. I played really well, so I’m really happy.”
The newcomer achieved the unexpected success as she played in only her fifth grand slam main draw. Victory took 73 minutes and featured 26 winners and five breaks of serve for Mertens.
The last Belgian to get this far at the Australian Open was Clijsters in 2013, a year after winning the trophy.