Peru and France have underlined the task facing the Socceroos at June's World Cup by recording 3-1 defeats in friendly action on Wednesday (AEDT).
Australia's two group stage opponents in Russia impressed with defeats of Iceland and the host nation.
Les Bleus were strong winners over an ill-disciplined Russian outfit.
Kylian Mbappe scored goals either side of a Paul Pogba strike, with Fyodor Smolov netting a consolation in St Petersburg.
Peru backed up their impressive 2-0 defeat of Croatia on Saturday (AEDT) by claiming another European scalp on American soil.
Renato Tapia opened the scoring in New Jersey after two minutes before Jon Guoni Fjoluson equalised before halftime.
After the break, Peru forwards Raul Ruidiaz and Jefferson Farfan found goals to keep the minnows on track to make an impact in Russia.
Denmark, the Socceroos' third opponent, shared the same result as Australia, recording a goalless draw with Chile.
It's one of the reasons that Michael Bridges, a commentator with World Cup broadcaster Optus, believes the South Americans will be a trickier opponent than the Europeans.
"They're a very hard, aggressive pressing team and like to win the ball high," he said.
"They don't absorb and invite pressure. They like to go out and win the game and I like them. They could be a team to watch, a real wildcard for the tournament."
Bridges' view is Denmark, which Australia will play after the opener with France, are beatable should the Socceroos contain key man Christian Eriksen.
"When I look at the group, Denamrk are a very well-structured team and that was very evident against Chile this morning," he said.
"They have two midfielders screening the back four and Eriksen playing in a free role.
"We were organised about Colombia and if we can do that against Denmark we're a real chance."
The Socceroos rode their luck in a 0-0 result in London against Colombia, an improvement on last week's 4-1 drubbing by Norway.
FRIENDLY RESULTS FROM AUSTRALIA'S WORLD CUP GROUP
Russia 1-3 FRANCE - St Petersburg, Russia
DENMARK 0-0 Chile - Aalborg, Denmark
Iceland 1-3 PERU - New Jersey, USA
AUSTRALIA 0-0 Colombia - London, UK