The Bolton Wanderers midfielder picked up an injury during his country's training camp in Portugal before arriving in Egypt's coastal governorate Port Said.

"We never thought it was bad until we arrived [in Port Said]. We can only hope that his state improves before Monday," Nigeria team doctor Abdulkadir Muazu said.

"I cannot say categorically whether he will be fit to play or not, but we will keep monitoring him. At the moment he needs to rest and not aggravate the situation," he added.

Nigeria are playing in Group D alongside Ghana, Senegal and Zimbabwe.