Midfielder Lucas Biglia has become the latest Argentina player to be hit by injury problems.
The Argentine will is now fearing for his World Cup place after suffering a "severe" back injury while playing for AC Milan.
Biglia was substituted after 72 minutes of Milan's surprise defeat to bottom side Benevento in Serie A on Saturday. He now faces a race to be fit for the tournament in Russia, creating another problem for national team coach Jorge Sampaoli.
Milan said on Sunday that tests have revealed he has a "severe lumbar trauma" consisting of "a fracture of the transverse processes of the first two lumbar vertebrae."
Biglia will undergo further tests but such injuries normally take around two months to recover from.
The 32-year-old Biglia will miss the end of the domestic season, including the Italian Cup final against Juventus.
Argentina's first World Cup match is against Iceland on June 16.
Biglia featured in all seven matches as Argentina reached the final four years ago, when it finished runner-up to Germany.
Last week, doubts emerged over the fitness of Manchester City's star striker Sergio Agüero, another key player for the Albiceleste. The former Independiente forward underwent surgery and will miss the rest of the English Premier League season.