Adu joined Benfica in the summer of 2007 for around €1.5million, but has failed to make an impact at the Estadio da Luz.
The American spent last season on loan at Monaco.
Adu joined Benfica in the summer of 2007 for around €1.5million, but has failed to make an impact at the Estadio da Luz.
The American spent last season on loan at Monaco.
