The club returned to professional play with promotion to the 2. Bundesliga for a single season in 1988–89 with Bodo Hertlein as president, before finally returning for an extended run in 1990–91. Initially, they were perennial relegation candidates, struggling hard each season to avoid being sent down. However, under unorthodox trainer Wolfgang Frank, Mainz became one of the first clubs in German football to adopt a flat four zone defence, as opposed to the then-popular man-to-man defence using a libero.
