Rafael Nadal narrowly avoided joining the Australian Open's shock casualties on Wednesday as women's champion Victoria Azarenka became the latest star to fall in what has become a tournament of upsets.
A day after Novak Djokovic's three-year Melbourne reign was halted by Stanislas Wawrinka, Nadal also flirted with disaster before getting out of jail against smooth Bulgarian Grigor Dimitrov.
The 13-time Grand Slam champion, troubled by a huge blister on his racquet hand, went a set down against the exciting young prospect and, facing set points in the third, he was tottering.
But Dimitrov, 22, went just long on the first set point and Nadal saved another before the Bulgarian gave him a one-set lead when, gifted an easy winner off a net cord, he ballooned his forehand out.
"I was so lucky," admitted the Spaniard, who ran out a 3-6, 7-6 (7/3), 7-6 (9/7), 6-2 winner and will face either Roger Federer or Andy Murray in his 22nd Grand Slam semi-final.
Djokovic's defeat by Wawrinka, who will play Tomas Berdych in the semis, ensures that Melbourne will host the first Slam final not contested by two of tennis's "Big Four" since the 2010 French Open.
"I'm a bit shattered," said Dimitrov. "It's tough losing that match, my first (Grand Slam) quarter-final. I came out expecting nothing less than to win."
The women's contest has been even more drastically affected and there was an air of resignation rather than shock when Azarenka tamely followed Serena Williams and Maria Sharapova out.
The Belarusian world number two was unbeaten in two years at Melbourne Park but she was comprehensively dismantled by an inspired Agnieszka Radwanska 6-1, 5-7, 6-0.
"I'll be fine tomorrow. I'll be working tomorrow. It's not the end of the world. But I'm not happy with what I did today," said Azarenka.
It ends a sometimes unhappy run of 18 wins at the tournament for Azarenka, whose loud grunting and perceived gamesmanship has earned her critics as well as fans in Melbourne.
But it was a major scalp for Radwanska, who had lost all seven previous meetings with the Belarusian, and now goes into a semi-final with Slovak 20th seed Dominika Cibulkova.
The win also ensures the tournament will have a new champion with none of the semi-finalists - Radwanska, Cibulkova, Li Na and Eugenie Bouchard - having won before.
"It's hard to play someone I lost (to) so many times before. I knew she's a great player. Especially here, she was playing amazing tennis," said Radwanska.
Cibulkova reached only her second Slam semi-final when she also won big against a favoured opponent in the form of fast-rising Romanian Simona Halep.
Halep is set to break the top 10 in next week's new rankings, but she froze in her first Grand Slam quarter-final as the energetic Cibulkova dominated 6-3, 6-0 in one hour exactly.
"I had emotions, big emotions, and I couldn't manage this," admitted Halep. "Before the match I was very nervous and I didn't feel the ball at all. I couldn't move my body and I couldn't play."
In the night match on Rod Laver Arena, 17-time Grand Slam-winner Federer was playing Wimbledon champion Murray.