Adriano, 27, failed to return from international duty in Brazil earlier this month and was later found at his mother's house in Rio de Janeiro.

On Thursday he announced he plans to take a sabbatical from the game, citing stress from the pressures at Inter, and admitted he does not know when he will return.

Ronaldo, who played in the 2006 World Cup along with Adriano, said: "I am sad for the lack of respect for idols.

"We usually see famous people and a number of opportunists giving pieces of advice and judging in moments of difficulty.

"Day by day, I see saints on the television, people who believe they are perfect in the world. This problem is even more sad than Adriano's.

"Nobody knows what it is about. I am a big friend of his and I've been following what is going on. It is a difficult moment. I will do my best to help him."