Career
The defender turned professional with VfL Bochum in 1996 and remained with them for eight seasons as they yo-yo"ed between the top two divisions. On 9 August 2006, he transferred to Hannover 96, as part of the deal which saw Per Mertesacker move in the opposite direction. On 27 September 2008, Hannover 96 were scheduled to play Bayern Munich at the AWD-Arena.
However, shortly before the match began, Jiří Štajner accidentally injured Mario Eggimann"s eye in training.
He gave an eye-catching, determined performance as Hannover 96 ran out 1–0 winners. On 22 April 2009, Hannover 96 announced that they would not renew his contract.
Fahrenhorst left the club on 30 June 2009 at the end of his contract and joined MSV Duisburg until 30 June 2011, but on 17 August 2010 he signed a two-year contract with Football Club Schalke 04 World War II