This paper focuses on evaluating the impact of sports expertise as the embodied experience in a sports activity on the decisional process of an expert physical education teacher. Both qualitative and quantitative studies were applied within a mixed-approach using a single case study. A clinical didactics methodology was employed with three important tenses of the teaching practice (already-there, test, after-work). To understand the internal determinants that monitor the teaching practice of our participant, semi-structured interview was used, "in situ" filmed observation and content analysis. Results indicate that personal determinants, the experiential and embodied "already-there" related to sports expertise, have a significant impact on the "personal" relationship to knowledge and the bodily awareness. This can be noticed by the way knowledge is delivered through a high recurrence to direct physical ostension demonstration by the teacher's body. Sport expertise is a major determinant of teacher's pedagogical and didactical conducts resulting from a subjective decisional process.