 Clark was also the first head coach of the Dayton Triangles, an early professional football franchise that entered into the National Football League after Clark's playing and coaching careers for the team were over.At St. Mary's, Clark compiled an overall head coaching record of 12–4–1 in three seasons.Professionally, Clark coached the Triangles to an overall mark of 12–5, including back-to-back Ohio City championships in 1913 and 1914.