None of the top three seeds will feature in the semifinals of the ASB Classic tennis tournament in Auckland.
After top seed Fabio Fognini and third seed Karen Khachanov were bundled out in the second round on Wednesday, second seed Denis Shapovalov was upset in the quarterfinals on Thursday.
The Canadian world No 14 was beaten 7-5 6-4 by fellow young gun Ugo Humbert, of France.
Shapovalov, impressive in his second round victory the day prior, wasn't able to replicate that, double-faulting on both set points to hand Humbert a sizeable upset.
The result sent Humbert into a semifinal against John Isner, who suddenly became the favourite for his third title in Auckland.
The big-serving fourth seed from the US advanced to the last four with a hard-fought 7-6 7-6 victory over Brit Kyle Edmund in the opening quarterfinal.
After also playing two tiebreaks in a three-set win over defending champion Tennys Sandgren on Wednesday, 34-year-old Isner again held his nerve in the big moments.
Ranked 20th in the world and the 2010 and 2014 ASB Classic champion, Isner was a come-from-behind three-set winner in his one match against 21-year-old Humbert in July last year.
Another Frenchman is through on the other side of the draw. Fifth seed Benoit Paire came from behind for his 3-6, 6-1, 6-4 quarterfinal win over Australia's John Millman.
The 24th-ranked Paire will play Polish sixth seed Hubert Hurkacz in the semifinals.
Hurkacz eventually outlasted Spanish veteran Feliciano Lopez, bouncing back from losing a gripping second set to clinch a 6-4, 6-7, 6-4 victory.
Meanwhile doubles player Marcus Daniell kept New Zealand hopes alive as he and Austrian partner Philipp Oswald fought back to win their quarterfinal.
Daniell and Oswald were 4-6 6-1 10-7 winners over Denmark's Frederik Nielsen and Tim Puetz of Germany.
It left Daniell as the last Kiwi standing in the event, after the campaign of Artem Sitak was brought to an end.
First up on centre court, Sitak and Indian partner Divij Sharan were beaten in an incredibly close quarterfinal by Belgian pair Sander Gille and Joran Vliegen.
Sitak and Sharan won the first set 7-5 but lost the second set tiebreak and the deciding super-tiebreak to miss out on a spot in the semifinals.