With June looming as a defining month for the national team - there's a key FIFA World Cup qualifier against Saudi Arabia, followed by a friendly with Brazil and then the Confederations Cup - and Ryan and Langerak are running neck-and-neck.
Both will of course be named in Monday's preliminary 30-man squad - but beyond that, which way Postecoglou will sway is anybody's guess.
Ryan got the nod for the most recent outing, the 2-0 World Cup win over UAE, whilst Langerak was selected days earlier in the 1-1 against Iraq.
Both distinguished themselves, making the conundrum facing Postecoglou that much more challenging.
It's not a position 109-cap Socceroos veteran Mark Schwarzer would like to be in.
When asked who he'd select in his green and gold team, the iconic gloveman, turned TV pundit, simply couldn't make a distinction.
"Who do I prefer? I don't know, it's a tough one," he said.
"I am just glad I am not in the position where I have to make that call between the two of them.
"I think whoever Ange chooses will do really well, which means he's in a good position with whatever call he finally makes."
Ryan's run as the undisputed No.1 is now over, as he rebuilds his confidence on-loan with Genk after slipping out of favour at Valencia.
He's been a big hit in Belgium after arriving in January, whilst Langerak has been an impressive ever-present with Stuttgart, who have the chance to return to the Bundesliga as second-tier champions this weekend.
Schwarzer sees varying strengths and qualities in both.
"Mitch has had a tremendous season and it looks like he's on his way back to the Bundesliga, whereas Maty has had a stop-start time at Valencia, and needed to leave to get regular game time again," he said.
"Ange showed in the last two games that he had a certain way he wanted to play, and he felt like both goalkeepers would have their different strengths.
"Mitch probably deals with a higher balls slightly better than Maty, probably due to his physical presence .. he's that bit bigger and a bit taller.
"He played in that first game and then Mary came in for the second with Australia playing a higher line, which is more his game then it is Mitch's game.
"You can fully understand why Ange played his hand that way."
Schwarzer, who had his own rivalry with Zjelko Kalac, knows neither will have enjoyed being rotated, but they might have to get used to it.
"It's frustrating when you're not playing every match, and when the manager makes those types of decisions tactically," he said.
"You're not normally used to managers making those sorts of calls, but that's his prerogative."
Ryan, with 31 caps to Langerak's seven, is the first to admit that despite his overall pre-eminence under Postecoglou the position is up for grabs like never before.
"The boss keeps everybody on their toes, and nobody has their position totally secure," he said.
"He's demonstrated that a number of times, and you saw that during the last international break with the switch between Mitch and myself.
"Competition is good in any team, you see that with all the big football nations who can field two or three really good sides.
"No-one can afford to get comfortable, we are all pushing each other and pushing in the same direction