In his acceptance speech of the National Academy of Kinesiology's (NAK) 2008 Hetherington Award, Daryl Siedentop (2008) humbly declared: "I have had the privilege for many years to play a small role in the development of research in the field now universally referred to as sport pedagogy" (p. 10). That declaration encapsulates the manner in which he conceived himself: a physical educator who had "realized how important good physical education can be in the lives of children and how difficult it was to consistently provide good physical education." In this paper, the authors propose that Siedentop's professional and academic impact in his areas of specialization demonstrates a profound commitment to the philosophical tenets of progressive and liberal education. Although he was not trained as a philosopher, he provided a philosophical foundation to his lifelong work in sport pedagogy and physical education. Siedentop was, it could be contended, a philosopher in disguise. He was a physical educator who incorporated philosophical ideas into his daily practice, not only to articulate that practice more consistently at a theoretical level, but also to produce a more coherent program that would better serve its recipients. To make their case, the authors first explore the historical development and state of physical education Siedentop encountered when he entered the profession in the 1960s. That background allows the appreciation to the positions he took in relation to the central debates of that period and the manner in which they shaped his professional and academic career. The authors conclude the paper exploring his celebrated Sport Education pedagogical model, which coincides nicely with the key philosophic traditions of progressive and liberal education and through which he proves to have been a practical philosopher in disguise.