The Socceroos will face a capacity crowd full of Mexico fans at the Rose Bowl stadium in Pasadena on Saturday night (Sunday AEST) ahead of Popovic naming his 26-player squad.
The training squad is 30 players after Cristian Volpato's shock defection from Italy, though the attacker seems destined for a cameo at best in that game.
Rather than picking his final squad early like some other coaches, Popovic filtered an extended squad through a training camp, cutting some players and bringing others in later.
He has been personally meeting with players who don't make the squad.
"It's never nice for a coach in terms of what's coming up in telling some players that they won't be here, but when we started the journey and the process, we knew that we would come to this point," Popovic said.
"And the more players that we could bring into our squad, into our environment, we believe that we can make the squad better.
"And now we also have another player (Volpato) that's coming in very late that also gives us opportunity to improve the squad and make it stronger, so I'm happy with the process we have.
"I'm really looking forward to the game. I can't wait for the match, and then we need to make some decisions, and then we go to our base camp."
Mathew Leckie, who is yet to play under Popovic after a torrid injury run, is one veteran who can underline his selection case with a strong performance.
First-time call-ups Volpato and Tete Yengi will also have a point to prove if they earn game time.
Both Popovic and defender Harry Souttar indicated the friendly, likely in front of a capacity crowd of more than 75,000 fans, would be the perfect preparation for the World Cup, especially Australia's clash with the US.
"The game is a wonderful game, obviously unique history about this stadium, playing the host nation, Mexico, 70,000-plus people," Popovic said.
"So it will really feel like we're here for the World Cup now, although we're a couple of weeks away.
"We've had players in at various times in the last three weeks. We're working on our game.
"We're delighted we have such a top opponent to showcase ourselves and see how we have progressed so far and what room we still have left to improve before we play Turkey."
After the squad, due to FIFA on June 1, is submitted, Australia have a friendly against Switzerland on June 6, before starting their group stage matches against Turkey, the US and Paraguay.
