Postecoglou has confirmed Palace skipper Jedinak will pull on the armband for the game at The Den on Thursday morning (AEDT).
The move to install Jedinak as the probable successor to Lucas Neill also casts doubt on the likelihood of Tim Cahill to start at the World Cup.
Neill led the team for their 1-0 friendly victory over Costa Rica - Postecoglou's first match in charge - but was omitted from the latest squad.
"It's a reward for him," the Socceroos coach said of Jedinak's appointment.
"He's playing in one of the toughest leagues in the world, captaining his club side and playing well.
"He's an outstanding candidate to lead us tomorrow night. Beyond that Mile is in the same boat as everyone else - he needs to continue to play well and continue to show form."
After all, a season spent chasing shadows against the Premier League's best is surely ideal preparation for daunting assignments against Spain, the Netherlands and Chile.
Mark Milligan, Postecoglou's captain at Melbourne Victory before his departure to the national team, is enjoying another strong season despite his club's inconsistencies.
Of the outsiders, potential debutant Massimo Luongo will have to impress Postecoglou in this week's training camp, while Jackson Irvine, Matt McKay and Oliver Bozanic all have an outside claim, although the latter more regularly plays as an attacking midfielder.
Chris Herd, capable of playing in defence and midfield, is also a candidate, but his unavailability for Aston Villa selection due to personal reasons and subsequent withdrawal from this squad may have ended his hopes of making the 23-man World Cup squad.
