Rafael Nadal suffered his first round-one exit at the Australian Open as Fernando Verdasco recorded a stunning five-set win at Melbourne Park.
The Spanish left-handers produced an exhibition of hard-hitting to thrill those inside the Rod Laver Arena over four hours and 40 minutes.
Verdasco saved a break point to prevent going 3-0 down in the decider, going on to win 7-6 (8-6) 4-6 3-6 7-6 (4-7) 6-2.
In the women's draw second seed Simona Halep suffered a shock defeat.
The 24-year-old Romanian was beaten 6-4 6-3 by Chinese qualifier Zhang Shuai, ranked 133rd in the world.
"I'm really disappointed," said Halep. "But it's only one day, only one match. Tomorrow, it's a new day."
She praised Zhang, adding: "She played without fear and she hit every ball. She had good rhythm."
Zhang, who will turn 27 on Thursday, burst into tears after securing her first victory in a Grand Slam at her 15th attempt.
She said she had "almost retired" last year after her ranking plummeted.
Once as high as 30 in the world, she dropped to around 200 and admitted she had felt "very sad every day".
As for Verdasco, he now meets Israel's Dudi Sela after hitting 90 winners and winning six straight games to clinch victory over fifth seed Nadal.
"I played unbelievably in the fifth set," said Verdasco, 32. "I don't know how I did it. I closed my eyes and everything went in."
Verdasco, beaten by Nadal in the semi-finals in 2009, showed grit to stay in touch when his compatriot threatened to dominate.
After surrendering a 5-2 lead in the fourth set, he dug deep to win the tie-break and take the match the distance.
At 2-2 in the decider, a glorious forehand - packed with the type of power he had showed throughout the contest - put Verdasco ahead and the world number 45 never looked back.
Nadal, who had beaten Verdasco 14 times in 16 previous meetings, talked about his game and the way tennis is changing following his loss.
"Everybody now tries to hit all the balls," said the 14-time Grand Slam winner.
"There are no balls that you can prepare the point. The game has become a little bit more crazy in this aspect.
"I was practising a little bit different, trying to be more aggressive. I can play defensive or offensive. But if you stay in the middle, then I am dead."
BBC tennis correspondent Russell Fuller:
"Wasn't that one of the most thrilling final-set performances we've ever seen? How he had the nerve to hit winner after winner was unbelievable. Phenomenal stuff from Verdasco. He was hitting the ball so hard."
Injuries and a 24-game decider
Verdasco's quarter of the draw produced some drama on day two of the first Grand Slam of 2016, not least on court 19, where Jeremy Chardy beat Ernests Gulbis 13-11 in a deciding fifth set.
Frenchman Chardy, seeded 30, edged through in temperatures around 31C in Melbourne and could now meet Verdasco in round three.
Fourth seed Stan Wawrinka is in the same quarter of the draw, but he will not have to worry about an early meeting with big-serving South African Kevin Anderson.
The 29-year-old, who knocked Andy Murray out of last year's US Open, trailed American Rajeev Ram before retiring hurt in the fourth set.
Wawrinka, who reached round two when opponent Dmitry Tursunov retired at the start of the third set, could meet Murray at the semi-final stage if the draw goes according to seeding.
Keeping retirement at bay
Lleyton Hewitt's tennis farewell will have to wait at least another two days after the Australian veteran beat fellow wild-card entry and countryman James Duckworth 7-6 (5) 6-2 6-4.
Hewitt, 34, announced last year that the Australian Open would be his final tournament and received the backing of a large contingent of fans at Rod Laver Arena.
"This is what I am going to miss the most," said the former US Open and Wimbledon champion, referring to the crowd.
On the emotion of the occasion, he added: "It was a tough situation, to try to block it all out. I tried to stay in the moment as much as possible."
Hewitt meets Spanish eighth-seed David Ferrer in the second round on Thursday.
Guarding against a grind
Tenth seed John Isner, one of the biggest servers in the game, is a potential threat to Murray at the quarter-final stage and slammed 37 aces as he beat Jerzy Janowicz in straight sets.
Isner is one of eight Americans in round two - the most since nine progressed in 2009.
Elsewhere, 13th seed Milos Raonic explained he now wears a mouthguard during matches to prevent him from grinding his teeth.
The 25-year-old, who beat Frenchman Lucas Pouille in straight sets, says grinding his teeth causes "stress and headaches", adding: "I guess maybe it's just a way to calm myself down."
Wimbledon runner-up progresses
In the women's draw, Garbine Muguruza, beaten by Serena Williams in the Wimbledon final last year, looked in complete control as she overcame Anett Kontaveit 6-0 6-4 in just 60 minutes.
And 2008 French Open champion Ana Ivanovic improved on her first-round exit last year by beating wildcard Tammi Patterson 6-2 6-3.
Still going strong
Radek Stepanek became the oldest man to win a match at the Australian Open in more than 38 years.
The Czech qualifier, who is 37 years and 65 days old, defeated Japan's Tatsuma Ito 6-4 6-3 6-7 (5) 6-2 to advance to the second round.
Stepanek, ranked as high as eight in the world, is the oldest player to have won a match at the Australian Open since Bob Carmichael - 38 years and 183 days - and Ken Rosewall - 44 years 62 days - in 1978.