"Persons in the shadows" may substantially affect how an individual acquires expertise, through, for example, guiding deliberate practice. In the domain of popular music, such persons in the shadows might be peers, parents and teachers. Little research exists on how individuals perceive the impact of persons in the shadows on expertise development, particularly in fields like popular music. This study investigates the perceived impact exerted by peers, parents and teachers on the expertise development of guitarists in the domain of popular music. Interviews were used to investigate nine case studies of guitarists with different expertise levels (experts, sub-experts, amateurs). The main focus was on the roles of "persons in the shadows" concerning practising, learning and motivation. The results show that experts differ from sub-experts and amateurs in the perception of support from persons in the shadows. In particular, peers and the formation of bands were thought of having a strong effect on practising, learning and motivation. The impact of parents and teachers on the expertise development in guitar playing was perceived as more ambiguous, and they were deemed as less important by the expert group.