Herrmann attended Purdue University, where he played for coach Jim Young's Boilermakers teams from 1977 to 1980.
Herrmann had an impressive college career; in 1980 he was recognized as a consensus first-team All-American, he was selected as the Big Ten Conference's Most Valuable Player, and he finished fourth in voting for the Heisman Trophy.
In 1982, he appeared in two games, but at the end of the season he was traded to the Baltimore Colts as part of the deal that brought John Elway to Denver.
In 1985, he was traded to the San Diego Chargers, where he played for three seasons and performed well as the backup to Dan Fouts.
Herrmann appeared in just 40 games during his 11-year pro career, completing 334 passes in 561 attempts (59.5%) for a total of 4,015 yards.