Keegan was greeted by warm applause from a 33,000 crowd but Barbarez scored the only goal of the game for the German side after a mix-up in the City defence.
In an exciting game Nicolas Anelka and Sylvain Distin were in superb form for City and must have impressed the 4000+ City fans in the crowd.
City: Nash, Distin, Horlock, Huckerby, Berkovic (Shuker 45), Sun Jihai, Dunne(Charet 45), Howey, Wright-Phillips, Anelka.
City travel to Rochdale for their next pre-season friendly on Monday evening.