Real Madrid's €50 million ($56m/£45m) signing Eder Militao was forced to cut short his unveiling at Santiago Bernabeu after a bout of dizziness on Wednesday afternoon.
The 21-year-old signed a six-year deal with the Blancos back in March and officially ended his time with Porto at the end of the 2018-19 campaign.
The Brazil international impressed during his first full year in European football, having moved to Estadio do Dragao from Sao Paulo last summer.
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Militao was Zinedine Zidane's first signing of his second reign at the Bernabeu and he has been tipped to make a big impact for Madrid in defence next season.