They squandered a bagful of chances in a one-sided first half and were punished when Tommy Rogic scored out of nowhere, his first off-target shot bouncing off a defender's back and his rebound slipping in under keeper Bernd Leno.
"One thing we won't underestimate is their ability to play the kind of football they've been renowned for".
"Second half was better".
"As much as you try and set up the team to be fearless in terms of where we want to defend, it's human nature that we fell back a little bit and probably gave them a little bit too much room and respect", he said.
That team is out of the automatic qualification places to return to Russian Federation for the World Cup next year with two matches remaining in the group stage.More news: Saudi Authorities Detain Three Iranian Revolutionary Guards
"We can't just expect that everything will function seamlessly", he said.
"So if people are easily dismissing that, they'll dismiss everything else", Postecoglou continued.
After being comprehensively beaten 4-0 by Brazil in a friendly on Tuesday, Australia has arrived at the eight-team Confederations Cup on a low.
And it didn't take the scratch line-up long to click as Lars Stindl latched onto a pass from Brandt to open the scoring with just five minutes on the clock.
Germany immediately went in search of a third goal after the break and got what they were after in the 48th minute when Goretzka beat Mathew Ryan with a powerful volley after a brilliant pass form Joshua Kimmich. However, even with a lot of individual qualities, it remains to be seen how they'll perform as a unit.
Australia is taking the trip to Russian Federation far more seriously, bringing a full-strength squad unlike Germany.More news: Trump slams obstruction of justice story on Twitter
A much improved second half from the Socceroos prevented the match from turning into a blood bath as once Ange Postecoglou's men were made to chase the game from the get-go.
With a record 48-goals for the Australian side, Cahill will look to add to his global goal-scoring tally against the world champions.
Low's side continued to dominate play after their early opener and Sandro Wagner almost doubled their lead in the 16th minute, sending a diving header inches wide at the far post following Goretzka's pinpoint cross, before the Hoffenheim man fired just wide again minutes later after beating the offside trap.
It was extended further three minutes into the second half.More news: LA Clippers building stadium in Inglewood