Cahill has been snubbed by coach Bert van Marwijk in two games in Russia, prompting public outcry in Australia about the 38-year-old not being used.

But Milligan, who has also leapt to the defence of the Socceroos' public whipping boy Robbie Kruse, says Cahill is an "unbelievable" asset to the squad.

A dislocated shoulder to Andrew Nabbout, who started as Australia's frontman in the two games, has paved the way for Cahill's possible return in Tuesday's tournament-defining game against Peru.

The Socceroos must beat the Peruvians, and France must down Denmark, for the Australians to have a chance of advancing into the knockout stage.

Cahill, Australia's leading all-time scorer, has been an unused substitute in both previous games as he seeks to become just the fifth player to score a goal at four consecutive World Cups.

"We have three strikers that are trying to compete at the minute to put their hand up for this next match," Milligan told reporters in Kazan.

"I guess all the talk about Timmy and everything, you guys don't see what we see in camp.

"While I'm sure, undoubtedly, he's frustrated that he has not had his shot yet, the amount of help that he gives to the players around him... is unbelievable.

"What happens on Tuesday, I'm not sure. What I do know is if Tim is called upon he'll be more than ready."

Milligan also defended the maligned Kruse from another wave of social media criticism about his performance against the Danes.

Kruse was substituted in the 69th minute and many fans have called for 19-year-old Daniel Arzani to take his starting spot.

"Robbie, as we all do, we probably don't read into those things too much," Milligan said.

"It's much more important what we think of each other than what everybody else thinks of us because ... when we're out on the field, we're the only ones that can help us.

"Robbie has been absolutely fantastic for a long time for us and I'm not the only one who thinks that, that is the main thing.

"We have got a very, very important game coming up and I know he and all of us will be ready.

"It's unfortunate that some people sometimes forget that at the end of the day, it's just a game.

"We're doing our very best to entertain and represent our families and our country ... we have to have thick skins but it's disappointing that people forget that we never go out to do bad."

Australian Associated Press