[1] Franz was born in Merseburg, East Germany, and grew up in Langenstein near Halberstadt, where he began his football career, and joined 1.

In Wolfsburg, Franz distinguished himself through his strong tackling, winning 63 percent of his challenges, making him the club's best player in this respect.

Together with Mario Eggimann, he formed the central defence of Karlsruhe's starting eleven, and with his Bundesliga experience, he played a crucial role in the club's promotion to the top flight.

On 24 June 2011, Hertha BSC announced they had signed Franz on a three-year deal,[2] but due to frequent injury, made only seven appearances in his first season in Berlin.

[3] In the 2007–08 season, Franz was openly criticised for his play style, distinguished by hard challenges and continuous provocation of opposing players.

In April 2011, Werder Bremen captain Torsten Frings and manager Thomas Schaaf criticised Franz for having elbowed Denni Avdić in the face during an aerial challenge.