The 22-year-old has signed a five-year contract with the Spanish side.
Ruiz failed to make an impact at Napoli after joining the Italian side from Espanyol in 2010.
Ruiz have earlier this summer been linked with a move to Manchester City.
The 22-year-old has signed a five-year contract with the Spanish side.
Ruiz failed to make an impact at Napoli after joining the Italian side from Espanyol in 2010.
Ruiz have earlier this summer been linked with a move to Manchester City.
