He played six years of varsity football and gained fame as one of the stars of Fielding H. Yost's "Point-a-Minute" teams that outscored their opponents 1,211–12 in 1901 and 1902.

One of the highlights of Herrnstein's playing career was the 1902 Michigan – Ohio State game when he scored five touchdowns in an 86–0 rout of the Buckeyes.

[3] In 1905, Herrnstein was hired as the head coach of Purdue and led the Boilermakers to a 6–1–1 record.

The 1906 Buckeyes did not allow a single touchdown, outscored opponents 153–14, and compiled a record of 8–1.

In 1908, Michigan's athletic director, Charles A. Baird, published a column about the upcoming football season and wrote the following of Herrnstein: "Herrnstein was a former Michigan star who is thoroughly acquainted with the Yost system and by several years of coaching at the Haskell Indian school, Purdue and Ohio State, has developed into a great teacher of football.

"[4] In 1909, Herrnstein's Ohio State team was 7–3, but lost its fourth straight game to Michigan, this time by a score of 33–6.