Napoli forward Jose Callejon described Cristiano Ronaldo as the best player in the world, claiming the Real Madrid star is the most complete footballer.

Callejon weighed into the Ronaldo and Lionel Messi debate ahead of Napoli's trip to Madrid for the first leg of their Champions League last-16 tie on February 15.

And Callejon favours his former Madrid team-mate - the winner of four Ballon d'Or awards among other individual and club honours - as the pair prepare to reunite at the Santiago Bernabeu.

"In my opinion it's Cristiano," Callejon said when asked to name the best player in the world during a Q&A session via UEFA's Instagram page.

"I think he's the most complete player out there."

Callejon is set to return to the Spanish capital for the first time since leaving Madrid for Napoli in 2013.

The 29-year-old Spain international emerged from Madrid's youth system and made more than 50 appearances following his debut in 2011.

But it is a homecoming Callejon is not relishing against the Champions League titleholders.

"I have mixed feelings," he said. "I feel happiness because I am coming home, but I didn't want to meet them so early into the competition, as they are the reigning champions.

"I am nonetheless sure it will be a special game. I have good memories of my time playing for Real Madrid in the Champions League, including when the club won the competition."