In 2002, Keller joined Eintracht Trier, where he spent two seasons, establishing himself as first-choice 'keeper in his second season, before signing for Hansa Rostock in 2004, where he didn't make a league appearance in two years, serving as understudy to Mathias Schober. In 2006, he joined Erzgebirge Aue, in a straight swap with their keeper Jörg Hahnel. Initially he was on the bench, but won his place when first-choice 'keeper Tomasz Bobel was sent off in the 12th game of the season. Keller remained in the team until March 2008, when he missed a game to attend the birth of his daughter.
