Lachner began his career at the Munich-based worker's football club FT Gern in the Arbeiter-Turn- und Sportbund championship.
In 1934 Lachner left Munich and joined Eintracht Braunschweig, where he played for the next 15 years.
After retiring from top-level football in 1949, Lachner continued for a time as player-manager at MTV Braunschweig in the Amateuroberliga Niedersachsen.
[1] During the 1950s and 60s, Lachner also worked as a football manager, including three stints at VfL Wolfsburg.
Lachner was capped eight times for the Germany national team, scoring four goals.