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Koulibaly has established himself as one of the best centre-backs in the world and the Napoli star has been linked with Premier League giant Manchester United.

Napoli and runaway Serie A leader Juve will go head-to-head at Stadio San Paolo on Monday, and Capello likened the Senegal international to five-time Ballon d'Or winner Ronaldo.

"The Ronaldo of Napoli? Without a doubt it's Koulibaly," Capello told Il Mattino.

"He's a monstrous, talented defender. Right now, he's among the best in the world."

Koulibaly has made 23 Serie A appearances this season - 33 in all competitions - for Napoli, who are second and 13 points adrift of Juve.

Napoli are also set to face Salzburg in the Europa League round of 16 in March.