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Sergio Aguero was taken to hospital after fainting at half-time of Argentina's friendly defeat to Nigeria in Russia on Tuesday.
Argentina coach Jorge Sampaoli said the Manchester City striker "got dizzy" during the break after his tap-in doubled La Albiceleste's lead.
The Argentine Football Association wrote on Twitter that Aguero "presented symptoms of fainting and for that reason he was taken to have routine studies done as a precautionary measure."
Dario Benedetto replaced Aguero in the lineup, but Nigeria rallied with three second-half goals to win 4-2, handing Argentina their first friendly defeat since November 2014.
Aguero's goal moved him past Hernan Crespo for third on Argentina's all-time top scoring list with 36 goals. He only trails Lionel Messi (61) and Gabriel Batistuta (54).
He has now scored in consecutive games for Argentina after not scoring in his previous eight, dating back to the 2016 Copa America.