ASB Classic organisers in Auckland could have been forgiven for having a heart attack on Wednesday as top seeds tumbled out of the tournament like tenpins.
It had been billed as a day of champions in which the top four seeds and a raft of former champions hit the court for second round matches in front of a packed crowd.
Instead, it started with defending champ and top seed Roberto Bautista Agut pulling out with a stomach bug, while sixth seed Feliciano Lopez also withdrew from his clash with Jeremy Chardy.
Then in the first match of the day, No.3 seed David Ferrer crashed out in a tense three set match with Dutchman Robert Haase, losing 2-6 6-4 7-6 (7-4).
However, by day's end it was not so bleak for the tournament's seeds with No.4 seed and last year's finalist American Jack Sock among those making it through.
Sock's powerful forehand sent US qualifier Ryan Harrison scrambling to all corners of the court in the night match as he won 7-6 (7-5) 4-6 6-1.
However, like those before him Sock did not do it easy as Harrison broke his serve twice in the second to claim the set, before a rejuvenated Sock raced away with the match in the third.
"Ryan is a very good player," Sock told the crowd after the game.
"(He) makes you play a lot of balls. His defence is incredible."
"(But my) forehand kept me in it today as it usually does. I've got to clean up a few things for the next match, but hopefully I can play a few more this week."
Sock now meets Frenchman Jeremy Chardy in Thursday's quarter finals.
Also through was No.2 seeded John Isner, but only just, as he survived a huge scare from Tunisian Malek Jaziri to win 6-3 3-6 7-6 (8-6).
Isner made his move late in the third set tie break, slotting home three successive backhand volleys to win the match.
Yet No.56 ranked Jaziri will be disappointed not to have walked away with a major scalp after producing stellar serving and blistering passing shots.
Also making it through to the quarters was entertainer and No.8 seed Marcos Baghdatis, who played an exciting match against German Dustin Brown to win 4-6 7-6 (7-4) 6-4.
The Cypriot and former Australian Open finalist not only produced dazzling shots but shared a laugh with Brown when the German almost did the splits chasing a ball.
Baghdatis now meets 2015 champion Jiri Vesely in Thursday's quarter finals, while Isner plays compatriot Steve Johnson.