Croatia-based Mrcela left Australia for the land of his ancestry at the age of six, and has yet to represent the green and gold at any level.
Mrcela was taken aback by the fervour and ferocity of life under Ange Postecoglou during his maiden camp, before the 2-1 World Cup qualifier win over Kyrgyzstan, in June.
Now, Mrcela wants to take his game to a higher plain, as Postecoglou plans to unveil his squad next week for the matches at Perth's NIB stadium on 3 September, and in Tajikistan five days later.
"I am training hard. I got back to Croatia with a lot of information on the things I have to improve on in my game from my first call up," Mrcela said.
"I am working on that. I was a replacement for (the injured) Trent Sainsbury last time and we will see what happens, but I am know I am there among the top 25 or 26 players.
"I am working on my conditioning, my body and the intensity I train at and play at to make it a higher level than you see in Croatia, which means I am working that bit harder than players do here."
Mrcela, 24, plays his club football for NK Lokomotiva Zagreb. He signed a four year deal there after his previous club, Krvatski Dragovolijac was relegated from the Croatian top division.
His performances were good enough to earn the move which kept him in the top division, and ultimately impressed Ange Postecoglou enough to integrate him into the Socceroos set up.
Mrcela is competing with incumbent starters Matthew Spiranovic, and Trent Sainsbury, for a spot in starting side.
If that wasn't difficult enough, Alex Wilkinson, who played every match at the World Cup and who has grown more and more comfortable at international level with each game, and Preston North End's Bailey Wright, are also in Postecoglou's plans.
"Playing for the Socceroos is a step up. There was more intensity in that Australia camp than you generally see in Croatian football," Mrcela said.
"Being in Dubai as part of the squad for 10 days and then going to Bishkek for the qualifier was fantastic.
"I learned lot and trained with some great players, it was a big experience for me. I hope it's not the last time for me. I want to be involved every time."
Perth-born but Croatia raised, Mrcela has played for six clubs and is looking to take the next step in his career, eyeing a move in the final weeks of the transfer window.
He made 20 appearances last season for NK Lokomotiva Zagreb, but this is a man in a hurry.
NK Lokomotiva Zagreb, which fell short of reaching the knock out stages of the UEFA Europa League, has made a faltering start to the new season and lies eighth in the 10-team Croatian First Football League with just four points from its first five games.
"There's a possibility I could move, even though I am focused very much on my club. We will see what happens," Mrcela said.
"There may be some chance of going to Turkey but nothing is concrete yet. That would interest me for sure.
"I really would like a new challenge and to go from Croatia to a foreign country to see where I am at."
“We are aiming for the Europa League this season. We have the quality to be up there challenging.
"We can do the same as last year or even better, maybe a top three finish. We have a better squad than last season, so the expectations are pretty big."
Mrcela missed out on a debut in Bishkek as Postecoglou went for the tried and tested defensive pairing of Wilkinson and Spiranovic. But he remains convinced Australia will make it nine points from nine by beating both Bangladesh and Tajikistan in its next two qualifiers.
"The Tajikistan game in particular will be hard, it will be very similar to Kyrgyzstan, where you have the fans pretty hyped up and yelling for their team," Mrcela said.
"But I am sure we are going to be the better side and will pick up six points from these coming games, for sure.
"We were a little surprised how well Kyrgyzstan played, especially going down a goal early there.
"But it was tough, bumpy pitch and we couldn’t play our football. But we got three points, that’s the most important thing."
