The Socceroos will play their second World Cup qualifier against Lebanon without injured duo Jordy Bos and Riley McGree, with full-back Joel King rushed into Graham Arnold's squad as cover.
McGree and Bos failed to finish the first half of Thursday's 2-0 win over Lebanon in Parramatta and won't take the field for the rematch in Canberra on Tuesday.
Having battled a foot injury this season, McGree was forced off the field early on, with Bos succumbing to a knee problem soon after replacing the Middlesbrough midfielder.
"McGree and Bos were sent for scans following the match, with the Socceroos’ medical team now in consultation with Middlesbrough (McGree) and KVC Westerlo (Bos) on treatment plans," the Socceroos said in a statement.
"There has been no return to play timeline set for either player, with both Bos and McGree to be reviewed by club medical staff on their return."
With Aziz Behich already sidelined, Australia were left with no natural left-backs in the squad. Centre-back Kye Rowles played out wide on Thursday.
Sydney FC left-back King has four caps.
Midfielder Keanu Baccus is suspended for Tuesday's game, in which a win will guarantee Australia’s passage to the final round of World Cup qualification.
The Europe-based Socceroos will leave Bruce Stadium straight after the game to catch a Wednesday morning flight out of Sydney and back to their clubs.
April shapes as a defining month for several Socceroos, with up to nine of the squad vying for promotion to one of the world’s top-five leagues.
Chief among those is influential midfielder Jackson Irvine, who has spent most of his career in Scotland and the lower leagues of Germany and England.
The 31-year-old’s club side St Pauli, where he plays with fellow Australia international Connor Metcalfe, sit top of Germany’s second division and are eight games from being elevated to the Bundesliga.
“It’s a testament to the kind of perseverance that a lot of guys have,” Irvine told AAP.
“I was always playing in the second leagues and waiting for the opportunity to compete at the highest level.
“(At St Pauli) we’re enjoying the ride and it’s nice to be part of a team that has a strong winning mentality. We want to achieve great things.
“Whatever happens between now and the end of the season, we have given ourselves a chance - and for Australian football that’s what we want to see.”
Among the Socceroos used by Graham Arnold over the last two years, only two are currently signed to a club in the top-five leagues of England, Germany, France, Spain and Italy.
Goalkeeper Joe Gauci has yet to play for EPL side Aston Villa since leaving Adelaide in January, while midfielder Denis Genreau has been troubled by injury all season at French club Toulouse.
One-cap centre back Alessandro Circati’s club side Parma sit top of Italy’s second tier.
Circati, 20, was considered so crucial to Parma's hopes of getting back to the top flight his club have played hardball when it comes to releasing him for next month's under-23 Asian Cup, which doubles as an Olympic qualification tournament.
The English Championship, however, is the league from which the Socceroos could spawn six Premier League players.
Harry Souttar's Leicester are entrenched in a three-way battle with Leeds and Ipswich for the two automatic promotion spots.
Ipswich, who boast retired Socceroo Massimo Luongo and centre-back Cameron Burgess, are in third place, a point behind Leicester and Leeds.
A late run from 10th-placed Middlesbrough - currently seven points off the crucial top six - could put Sammy Silvera, Tom Glover and McGree in the play-off places.
