West Ham's Argentina midfielder Manuel Lanzini will miss the World Cup after suffering a ruptured anterior knee ligament injury in training.
Lanzini was named in Jorge Sampaoli's 23-man squad last month.
The 25-year-old made 27 appearances for West Ham in the Premier League last season, scoring five goals.
Argentina begin their World Cup campaign against Iceland on 16 June before games against Croatia and Nigeria in Group D.
Lanzini started Argentina's 4-0 friendly win over Haiti last week.
Ever Banega, Lucas Biglia, Angel Di Maria, Giovani Lo Celso, Cristian Pavon, Maximiliano Meza and Eduardo Salvio are the other midfielders in Sampaoli's squad.
Sampaoli is already without Manchester United goalkeeper Sergio Romero, who also a knee injury, and has replaced him with Tigres' Nahuel Guzman.
Argentina have yet to announce a replacement for Lanzini.
[PARTE MÉDICO] Manuel Lanzini sufrió, en el entrenamiento matutino de hoy, la rotura del ligamento cruzado anterior de su rodilla derecha. pic.twitter.com/lmYEVr5YaV— Selección Argentina (@Argentina) June 8, 2018