Argentine striker Sergio Aguero is out of the World Cup after suffering a muscle tear in the 3-2 victory over Nigeria, a Buenos Aires newspaper reported on Thursday.
Aguero's injury, which could not be immediately confirmed by team spokesmen, would be a major blow to the South Americans' campaign to capture a third World Cup, this time on the soil of their great rivals Brazil.
"This morning the worst news was confirmed. He has a tear and won't be able to play any more in the cup," Clarin said on its web site.
The Manchester City forward, part of Argentina's so-called "Fab Four" of strikers, was taken off during the first half of the match against Nigeria that gave them top spot in Group F.
Coach Alejandro Sabella said afterwards he had a muscle problem. Argentine TV channel TyC Sports said the tear was on a muscle in Aguero's left leg.
More information was expected at an Argentine training session and news conference in Belo Horizonte at the end of Thursday afternoon.
Nicknamed "Kun" after a Japanese cartoon character, the 26-year-old is a close friend of national captain Lionel Messi and is also the father of Diego Maradona's first grandson.
Argentina next play in Sao Paulo on July 1, a last 16 knockout game against Switzerland. Fellow strikers Ezequiel Lavezzi or Rodrigo Palacio could take Aguero's place.
"We have forwards of the same style as Aguero and others, with a different style, like Lavezzi, who came in and handled himself well on the wings and helped us cover spaces," Sabella said after the Nigeria game, where Lavezzi replaced Aguero.