Müller is a journalist who has worked for several printed and digital newspapers as the magazine Hoy (Chile), Diario16 y La Gaceta de los Negocios (Spain), and also El Universal (Venezuela) where he was executive director. He was part of El Mundo from its founding, where he became deputy director until he left the newspaper in 2014. Since then he is columnist and deputy director of El Español. Müller is the author of “Leones contra dioses”.