'Osky' had to be replaced during his side's quarter-final victory over the Netherlands after injuring his foot while attempting to meet a long ball.
Replacement Sergio Romero will now take the reins for the semi-final and beyond after it transpired that Ustari's injury is extremely severe.
The ex-Independiente man, who has also represented the albiceleste at full international level, will be out of action for eight months.
This is a source of great consternation for his club side, Getafe CF. Club president Ángel Torres admitted that it was now unlikely that Osky would be able to play for the Azulones at all this season.
The 22-year-old served as understudy to his veteran countryman, Roberto 'Pato' Abbondanzieri, but the search will now be on in Madrid to find a replacement for him.
Steve Michaels, Goal.com