Background: Emotions are inherently intertwined with learning and disciplinary identity, and this relationship demands that teachers attend and respond to students' emotions. In this study, we forward a theory that the development of "pedagogical empathy," or the capacity to understand the implications of student emotions and use emotional data to make adaptive pedagogical decisions, is a component of adaptive expertise. Methods: Using qualitative methods to analyze the discourse in eight debrief discussions among secondary mathematics teachers following rehearsals of practice, we examine how teachers used this opportunity to generate and use emotional data in support of the development of pedagogical empathy. Findings: We found that rehearsal debriefs provided an opportunity to make emotional data available to participants in three ways and that teachers then used that emotional data in six ways across the debriefs. Student emotions, both from teachers in the position of students and in consideration of hypothetical students in the classroom, were pervasive in the debrief discussions. Contribution: After considering the ways in which emotional data were made visible and used, we return to theory to consider how these highlight the opportunities rehearsals offer to develop pedagogical empathy and discuss implications for teacher education and future research.