 In the following three seasons combined he rarely missed a game, adding four goals, but Mainz would be relegated in 2007.In July 2007, Friedrich moved to Bayer 04 Leverkusen, continuing to be an everpresent defensive unit and contributing – early in his first year – to consecutive home wins against Karlsruher SC (3–0) and VfL Bochum (2–0).He scored ten league goals in his first three seasons combined.