Demling grew up in St. Louis, Missouri beginning to play soccer when he was seven at St. Thomas More parish in the C.Y.C.
In 1973, the expansion San Jose Earthquakes of the North American Soccer League (NASL) selected Demling with its first draft pick.
However, he lost the entire 1975 season due to a broken leg suffered in the 1975 NASL Indoor Final.
In 1980, he left the NASL and signed with the San Francisco Fog of the Major Indoor Soccer League (MISL).
In 1999, Demling coached eighth-grade soccer at Blach Junior High School in Los Altos, California, taking the team to the Valley Junior High School Athletic League championship.