Nigeria stunned co-hosts Australia 3-2 on Thursday in the biggest shock of the Women's World Cup so far, while the United States failed to hit top gear in a stalemate with the Netherlands.
Australia's damaging defeat, having surrendered a 1-0 lead, leaves their last-16 hopes in real danger with one round of games to play in Group B.
Australia are a point behind and now must beat Olympic champions Canada on Monday otherwise they will be out of their home World Cup.
Emily van Egmond came into the side and she fully justified the decision of coach Tony Gustavsson by scoring the opener in the first minute of first-half injury time, rolling the ball smartly into the net.
But the lead lasted just five minutes because, in the sixth minute of added time, Uchenna Kanu popped up unmarked at the far post to prod the ball home and silence the vast majority of the crowd.
Defender Osinachi Ohale then pounced from close range with 25 minutes left to nod in from almost right on the goal line.
Things got worse for the Matildas seven minutes later when they made a mess of a routine ball over the top and Barcelona's Asisat Oshoala kept her head to score from a tight angle.
The United States beat the Netherlands four years ago to retain the World Cup and are now pursuing a third title in a row, something that has never been done before.
But they were far from their best in an entertaining 1-1 draw with the Dutch in front of a crowd of 27,312 in Wellington.
Their bid for a place in the last 16 also goes down to their final group game, against debutants Portugal.
Portugal defeated Vietnam 2-0 in the other match in Group E on Thursday.
England are the headline act on Friday when they play Denmark in Sydney.
Also on Friday, Argentina play South Africa and China face Haiti.