Defending Heineken Open champion David Ferrer has won his second round clash with American Donald Young to progress to the quarterfinals in Auckland.
The No 1 seed survived a scare when he lost the first set on a tie-break but battled back to win out 6-7 (5), 6-3, 6-1.
Ferrer will now face fellow Spanaird Guillermo Garcia-Lopez in the last eight of the tournament.
Events earler in the day were hardly what the competition organisers wanted: two of their biggest headline acts and four seeded players in total gone within hours of each other on a day of drama.
The previous week's women's professional event at the same venue dished up a dream final between the the tournament's two biggest drawcards, Ana Ivanovic and Venus Williams.
But hope that one of the glamour top seeds, other than four-time champion Ferrer or big serving American John Isner, and the most intriguing of the wildcard invitees would still be there at the business end of the tournament disappeared during a tense and humid day session.
At the end of the carnage, four of the top eight seeded players, including popular world No 12 German Tommy Haas and the most well known wildcard, former Grand Slam finalist Marcos Baghdatis, had departed the event.
The drama began at 10am when Baghdatis, the colourful Cyprus player and former world No 8, resumed his rain-interrupted Monday night opening round match only to be promptly bundled out of the tournament by unheralded American Steve Johnson who then went on to upset fourth seed Kevin Anderson of South Africa in the last match of the day session.
Granted a wildcard entry like Williams the week before, Bagjdatis was beaten in three sets by Johnson who made the main draw despite losing to compatriot Bradley Klahn in qualifying.
After gaining a "lucky loser" pass into the next round, the 160th ranked Johnson seized his opportunity to down the disappointing Baghdatis, nowadays more famous for this racquet-busting meltdown at the Australian Open, before blazing past a lethargic Anderson 7-5, 6-4.
Baghdatis was promptly followed out of the tournament by second seeded Haas who was granted a bye into the second round.
Earlier in the day, Klahn had caused the first upset of the week by tumbling out eighth seeded Daniel Brands. The sixth seed, France's Benoit Paire, followed soon after, easily beaten by Spaniard Roberto Bautista, 6-3 6-4.
But it was Haas's departure that was the talk of the session.
In a classic match-up of the young buck against the old bull, Haas found himself outclassed and outgunned by American wildcard Jack Sock who pulled off a major upset.
Spectators were stunned as the 21-year-old Sock, ranked 100 compared to Haas's No. 12, demonstrated raw power and nerves of steel to win 6-4, 6-4 in 72 minutes.
In their only previous meeting, at Roland Garros last year, Haas won in straight sets. But he cut a frustrated figure at Stanley Street yesterday, proving no match for his younger opponent.
Haas admitted afterwards that he was rusty and a decision not to play in the first week of the year so he could spend time with his family had not made for ideal preparation.
Sock will now face unheralded Spaniard Roberto Bautista Agut for a place in the semis.
"It's exciting, but I [need to] keep my head going forward and get ready for tomorrow," Sock said after the biggest win of his fledgling career.
Earlier, fellow countryman Johnson, ranked 160 in the world, had mowed down Baghdatis 7-6, 6-7, 6-4.
In other matches, flashy German Philipp Kohlschreiber, the tournament fifth seed, reached the quarterfinals with a comfortable 6-4 6-2 win over Argentina's Horacio Zeballos.
He will now face third seed John Isner in the quarters after the big American saw off Slovakian Lukas Lacko in a difficult encounter won 7-6, 3-6, 6-2.
The giant serving Isner admitted to still being troubled by an ankle injury that forced him to pull out of the Hopman Cup last week but didn't expect it to stop him playing his quarter final.
"I'd be lying if I told you it wasn't tender," he said. "It's very tender and it's wrapped very tight. Tomorrow morning is going to be really important to see how I turn out. I'm going to have ice on my foot for the rest of the day really."
Isner's serve wasn't just a threat to his opponent. Spectators were regularly dodging his 220 km/h plus rockets and a ball girl was struck by one fiery delivery that was clocked at 231 km/h.
"Sometimes I play and I'm worried about people in the crowd," Isner admitted. "I've hit people in the eye before and it's just terrible. Luckily for me [the ball girl] was tough as nails out there and she didn't flinch."
Klahn relished his first match on centre court yesterday, upsetting Brands with a 7-5, 4-6, 6-3 after they resumed their rain-interrupted first round match. But the 23-year-old, who qualified for the main draw in Auckland without dropping a set. But he fell in the second round later the same day, losing 6-7, 6-2, 6-3 to China-Taipei's Yen-Hsun Lu.
- Fairfax Media