[2] Both his parents[3] were of Danube Swabian descent (German: Donauschwaben) that were displaced from Yugoslavia after World War II.

His father was born in Bačka Palanka and his mother in Inđija, both towns part of the province Vojvodina in Serbia.

While at Stuttgart, Müller took part in UEFA Euro 1980 with West Germany, aged 22, after a brief taste of action at the 1978 FIFA World Cup, where he started all four games.

[4] He had a disappointing 1982 World Cup, and despite playing in the Italian league, he made his 42nd and last appearance for West Germany the following year.

[4][6] Müller was an official ambassador for the city of Stuttgart for the 2006 FIFA World Cup and Innsbruck at UEFA Euro 2008.