In this paper we analyze the reflection that emerges in future mathematics teachers when evaluating the management of contingent situations of the classroom work. The information retrieved from the stimulated recall, the semi-structured clinical interview and the video recording of the class are triangulated. We report through content analysis the results of two cases in which the reflection allows us to investigate and confront the visible measurable knowledge used for contingent situations management. The results show that future mathematics teachers manage the contingent situations according to the level of disciplinary knowledge they have. This knowledge allows them to perform better management in the class since it provides them, among others, better tools to investigate different types of teaching methods, utilization of sundry representations to teach a certain mathematical content, and anticipate mistakes and difficulties of the students