Massimo Luongo and Tomi Juric are tipped to start against Colombia at Craven Cottage on Tuesday evening, following the 4-1 loss to Norway.
 
With Mat Ryan rested, Brad Jones and Danny Vukovic will each get 45 minutes in the friendly encounter.
 
James Meredith may get a chance at left back, while Josh Risdon could feature after Bailey Wright struggled at right back.
 
"I came here with 26 players, two have gone home [Sainsbury and Jurman], we have 24," van Marwijk said.
 
"I told the players I cannot promise to let everyone play, this is a camp to see as much as possible. There will be a few changes, I like to see most of the players."
 
Ryan has been Australia's first-choice goalkeeper for the past four years since Brazil. But the new Socceroo coach said he has not decided yet on who will be his chief goalkeeper in Russia.
 
"This camp is to get to know each other," van Marwijk said.
 
"I said I want to see all three goalkeepers. They have got as good an opportunity as Mat to be number one."
 
Australia has been criticised for the heavy defeat at the hands of Norway, but the Dutchman said the result is "not the end of the world".
 
"You have to be disappointed when you lose 4-1," he said.
 
"But we have to go it's not the end of the world. I said a few words [to the team], and when I look at the team now, I think they are more open.
 
"The message was also that it's good that you listen to the coaches, but it's good that you have your own initiative, because the game can also change, things can go a different way.
 
"I think they understood it and we worked very well the last few days."