Small and medium enterprises (SMEs) are struggling competing in their respective markets while handling relationships with their main - often larger - customers. This paper argues that these new market challenges require the exploration of resource development patterns implemented in small suppliers, as they are engaged in upgrading key processes as required by large customers. To achieve this goal this paper i) develops a longitudinal single-case study of Gamma - a small Italian supplier in the mechanical sector - focusing on the analysis of the evolution of the interactions with its three key customers; ii) adopts the IMP approach on resource interaction to understand the variety and complexity of small supplier-large firm relationships. ...