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.
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.