Cahill's played 38 minutes since moving to Millwall FC in England's Championship, under former teammate, now-coach Neil Harris. 

This is in addition to the little-over 90 minutes Cahill played for Melbourne City this season, in a troubled season for the 38-year-old that has put his World Cup hopes in doubt.

"It's not a guarantee for him that I will nominate him for the world championship," van Marwijk told reporters.

"But for me it's also important to give him a signal that he's an important player.

"He didn't play a lot and it's important that players have rhythm and play," van Marwijk said.

"But there always are exceptions."

As the Socceroos' leading goalscorer - five caps away from equalling Mark Schwarzer's appearance record of 109 - Cahill has a lot riding on this World Cup.

If he makes the squad and scores, he'll join an elite group to have scored in four World Cups. But whether van Marwijk's truly equipped to leave Cahill out is another issue, with fellow striker Jamie Maclaren recently left out of the squad to face Norway and Colombia.

There are very few other striking options in van Marwijk's squad. 

"And he's a player who was very important for the national team in the qualification and in the play-offs.

"And it's a very good signal from him that he went to England to play to make a chance for the world championships."