In this article, we consider the potential influences of the study of proofs in advanced mathematics on secondary mathematics teaching. Thus far, the literature has highlighted the benefits of applying the conclusions of particular proofs to secondary content and of developing a more general sense of disciplinary practices in mathematics in relation to proof. Instead, we consider implications for secondary teachers that stem from the study of content within particular proofs in advanced mathematics. Illustrating with one example, we explore another way in which the study of advanced mathematics might be used to serve prospective secondary teachers.