Usually, NFL coaches have a history of playing football in college. Not always, but usually. And that’s true for Dirk Koetter, too, though his playing career is somewhat obscure. Apparently he was a highly recruited dual-threat quarterback at Idaho State way back in 1977, but injuries stopped his career from going anywhere. Which is why ESPN’s Kevin Seifert ranked his career as the 25th-best among all NFL head coaches. He’s not the worst!
Koetter saw some action as a freshman and opened the 1978 season as Idaho State's starter, but a separated shoulder in the season opener ended his season. The resulting surgery derailed his career. He played sparingly as a senior in 1981, completing 31 passes in 54 attempts for 349 yards, on a team that won the FCS national championship. An Idaho State biography from the time reported he was the "best student on the team" with a 3.6 grade point average.
Quarterbacks turning into offensive gurus isn’t exactly all that rare, and being the "best student on the team" explains some things as well. But Koetter never comes across as the most cerebral of head coaches, and usually defers to some common sense explanations in his press conferences, downplaying the complexity of the game. Football’s not rocket science, after all.