Nigeria say defender Uwa Echiejile is out of the World Cup with an unspecified injury.
The team said in a statement on Saturday from their training base in the United States that the Monaco left-back had a muscle tear and needed three weeks to recover.
The statement said Echiejile will be replaced by Ejike Uzoenyi, who was in Nigeria's preliminary World Cup squad but was initially cut from the final 23. Nigeria say FIFA has been informed of the intended switch.
Coach Stephen Keshi was quoted as saying there wasn't enough time to wait for Echiejile to recover.
However, England-based central defender Kenneth Omeruo will be fit for the game against Iran, the statement said, after an ankle injury sustained in a collision with a teammate at a training session last week. Omeruo had a scan on the ankle on Saturday.
Nigeria played the U.S. on Saturday in a final friendly for the African champions before they start their World Cup on June 16.