The ASB Classic has its first big upset, after Alize Cornet ousted second seed Petra Martic in three sets in the round of 16 on Wednesday.
Cornet dropped the first set but bounced back to prevail 3-6 6-4 6-4 to end her Croatian opponent - and good friend's - tournament.
The 57th-ranked Cornet was more consistent with her first serve and broke Martic on six occasions to advance to a quarter-final.
It was a blow for 28-year-old Martic ahead of the Australian Open.
She has climbed to a career-high in the rankings on the back of reaching the quarter-finals at last year's French Open.
Cornet has won six career titles but has always struggled at grand slams, failing to reach the last eight in 55 major appearances.
She has a chance to go deep in Auckland, however, placed on the opposite side of the draw to tournament favourite and top seed Serena Williams and teenage sensation Coco Gauff.
Americans Williams and Gauff will play their second-round matches on Thursday.
Cornet will advance to face American Jessica Pegula, who proved far too strong for Tamara Zidansk in their round of 16 clash, coasting to a 2-6 3-6 victory.
In other action, Canadian fan favourite Eugenie Bouchard booked her spot in the quarter finals with an impressive 6-4 6-4 win over Caroline Garcia.
American teenagers Catherine McNally and Couri Gauff coasted to a 6-3 6-2 win over Australians Jessica Moore and Arina Rodionova in their doubles match-up.
Local hope Erin Routliffe and American partner Allie Kiick took the opening set against defending singles champion Julia Goerges and Caroline Garcia, but soon found themselves on the wrong side of a 4-6 6-1 10-8 scoreline.
Rounding out day three, Amanda Anisimova continued her strong play with a 6-2 6-4 win over Daria Kasatkina.