This paper will present the progress of a research, framed in the ethnography of educational research, whose objective is to analyze the resignifications and transformations of the knowledge that integrate the Didactic Repertoire (Cicurel, 2016, Causa, 2012) and that allow its expansion-evolution during the period of the Practicum of the initial training of language teachers. We start from the idea that this internal mobilization of knowledge is produced by the contradictions and tensions that are generated in the circulation of knowledge between the training institution and the field of practice and that are manifested in the interaction between the teacher trainer and the student trainee. The role of the teacher, in this interactive process, on the one hand, is to orient and guide the student in the resolution of these contradictory situations and, on the other hand, to problematize situations and generate new contradictions that will lead the student to a transformation and construction of new knowledge, thus allowing the evolution of his didactic repertoire. In order to observe this problem, we analyzed a training device used in the subject of Special Didactics and Teaching Practices, of the Faculty of Arts at the University of Buenos Aires, Argentina. Our methodological tools were created based on the analysis of discourse in interaction and the application of an inductive-deductive, deductive-inductive procedure that allowed us to identify the knowledge mobilized during the training activity and to observe its transformations.