Real Madrid defender Sergio Ramos feels undervalued by sponsors Nike.

Ramos has blacked out his boots in recent weeks in protest against the way he's been treated, reports Marketingdeportivomd.com.

The Real captain believes he deserves a bigger contract from Nike given his profile and is now in the process of getting out of the deal.

Ramos is listening to offers from the likes of Puma, New Balance and Under Armour.

However, the only company that could match Ramos' demands is Adidas.