Argentina striker Joaquin Panichelli suffered a knee injury in training on Thursday, the national team said, with media reports suggesting he has torn his ACL less than three months before the World Cup.
The 23-year-old has only made one appearance for the World Cup holders but was expected to play in Friday's friendly against Mauritius.
Panichelli is the leading scorer in France's Ligue 1 this season with 16 goals for Strasbourg.
Argentina said in a social media post he would undergo medical tests to determine the extent of the injury.
But local media said he had torn his ACL and would miss the World Cup in the United States, Mexico and Canada which starts on June 11.
Argentina will start their title defence on June 16 against Algeria, before also facing Austria and Jordan in Group J of the expanded 48-team tournament.