The Spanish soccer federation didn't give more detail about the condition of the right back.
His absence comes as regular starting striker Álvaro Morata returned to practice after his own bout with the flu. Central defender Hugo Guillamón, nursing a knee issue, trained separately and was unlikely to be available for Wednesday's opening match.
Spain faces Costa Rica in its first game in Group E. It then plays against Germany and Japan.
Spain’s only World Cup title came in 2010 in South Africa. It made it to the final of the Nations League and the semifinals of the European Championship last year. Its last major title came at Euro 2012.
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