On 26 January 2011, FK Željezničar Sarajevo announced that Gerhardt was coming on trial with the club. He signed for FK Željezničar on 7 February, for the remainder of the 2010–11 season. After helping the Club win the National league cup he was awarded a 1-year contract, keeping him at the club until the end of the 2011/12 season.
Despite being born in Bern, Switzerland, Gerhardt accepted the call to play for the Liberian national team. He was eligible to play for Liberia due to his heritage. He debuted on 26 March 2011 in a 2012 Africa Cup of Nations qualification match against Cape Verde Islands, a 2–4 loss.