The 27-year-old missed his return flight back to Milan and since then no one – including the player's agent and his mother – heard anything about him.

Adriano has previously failed to report to Inter on time following international duty, but this time Mourinho is worried that something serious could have happened to the former Parma man.

"This is not indiscipline or a joke, it is much more serious," the Portuguese coach told reporters on Saturday.

"This is not an easy situation. We're not talking about a player who decided to come back a day later, or just missed his flight. It is much more serious than this."

Reports from Italy raised fears that Adriano could have been exposed to a kidnapping incident, as similar to a number of Brazilian footballers who were connected with ransom kidnapping in the past.

Manchester City's Robinho once had to pay a ransom of $50,000 to release his mother after she was taken as a hostage.

"We will have to wait and see how this all ends for him, but at this moment in time I am concerned about the man more than the player," Mourinho considered.

The ex-Fiorentina player's career has been marred by psychological problems which forced him to adopt an undisciplined lifestyle over the last few years.