Sergio Aguero was reportedly rushed to the hospital after he fainted in the dressing room during the halftime of the Super Eagles game on Tuesday.
According to Argentinian news outlet VarskySports, the Manchester City striker was sent away for an immediate check-up.
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They tweeted: "Kun Agüero fainted in the dressing room and was taken to a nearby hospital for a general checkup."
The news will come as a huge blow for Pep Guardiola with the Citizens due to face Leicester away at the King Power Stadium on Saturday.
Aguero started off the match in blistering fashion - causing Nigerian goalkeeper Daniel Akpeyi to pick the ball up outside the area as he closed him down.
This led to the match's opening goal, as Sevilla midfielder Ever Banega netted from the resulting free-kick.
The 29-year-old also netted for the South Americans in the eventual 4-2 loss against the Super Eagles,
but failed to come out for the second-half.