Keller played professionally for VfB Stuttgart, 1860 Munich, VfL Wolfsburg, 1.

[1] On 13 October 2010, Keller became interim manager of VfB Stuttgart until a permanent appointment had been found.

[2] He was replaced by Bruno Labbadia after two months in charge of the team on 12 December 2010.

[6] After only two wins in 10 matches in the 2014–15 season,[7] Keller was sacked on 7 October 2014 and succeeded by Roberto Di Matteo as head coach.

This biographical article related to association football in Germany, about a defender born in the 1970s, is a stub.