Ryan was withdrawn from the Australia squad which will face Bangladesh and Tajikistan after picking up an injury while playing for Valencia against Deportiva La Coruna.
The injury was described as a "knock", but Ryan explained on Twitter that he will undergo arthroscopic surgery to fix the knee.
Ryan was replaced in the Socceroos squad by Adelaide United goalkeeper Eugene Galekovic, leaving Ange Postecoglou with only his third, fourth, and fifth choice goalkeepers at his disposal.
Ryan's regular understudy, Mitchell Langerak, is also out for the next eight weeks after suffering an injury while training for his new club, Stuttgart.
“It’s a blow for Mat to miss these games but he picked up a knock in Spain overnight and with the travel distance and the lateness of his club game we have decided to bring in Eugene Galekovic,” Postecoglou said.
“Eugene is more than capable replacement and he will join us in Perth and we will move ahead without Mat.”
Adam Federici of AFC Bournemouth is now expected to start between the sticks, even though he has been on the bench all season after his off-season move from Reading.
Leyton Orient goalkeeper Alex Cisak, the squad's bolter, could also be a chance of making his international debut.
The Socceroos face Bangladesh on Thursday night, which can be seen on SBS.
