Argentina striker Sergio Agüero's continuing participation at the World Cup is shrouded in uncertainty due to the muscle injury that forced him off in Wednesday's win against Nigeria.
Agüero came off in the 38th minute of the 3-2 Group F victory in Porto Alegre and was anxiously waiting the results of tests to find out the extent of the injury.
"It has not been confirmed that it is a tear, it could be a strain," the Argentine team's press officer Andres Ventura told AFP on Thursday morning.
Agüero, 26, hobbled off the field to be replaced by Ezequiel Lavezzi, but Argentina coach Alejandro Sabella said only that he had a "muscle problem" after the match, while the player himself left the stadium without speaking to journalists.
"It is a muscle injury, as Sabella already said after the match. To go from that to saying that he might not be able to play again in the World Cup is nonsense," added Ventura, hitting out at reports published in Argentina about the severity of the problem.
A simple strain could leave Agüero on the sidelines for around 10 days, but a tear would likely keep him out for around two to three weeks, thereby bringing his World Cup to a premature end.
Agüero endured an injury-affected season in England with Manchester City and has not produced his best form so far at the World Cup.
His fitness adds to Sabella's concerns in attack, where Rodrigo Palacio is recovering from a minor ankle injury and Gonzalo Higuain is only getting back to peak fitness after a spell on the sidelines of his own.
The win against Nigeria took Argentina through to a last-16 tie against Switzerland in Sao Paulo next Tuesday.