Maicon set for knee surgery in Brazil
The Brazil international complained of pain during training in the morning and tests showed an injury to his meniscus, the club said on their website.
Inter, who face Lecce in their opening Serie A game on August 28, did not say how long Maicon would be sidelined.
The club recently signed fellow Brazilian Jonathan who plays in the same position.
Inter have already lost the services of Italy's reserve goalkeeper Emiliano Viviano for about six months after he suffered a serious knee injury during training last month.