Müller made his professional debut with EHC Klostersee of the 2nd Bundesliga in the 1997-98 season, before playing in the Deutsche Eishockey Liga (DEL) from 1998 to 2009.

It appeared impossible for Müller to play professional ice hockey any longer, but he recovered and made his comeback on 3 February 2007 at the DEL All-Star Game 2007.

Wick told the media that Müller was terminally ill and already exceeded the anticipated average life, as only 3% of the people having the same cancer live over five years.

[2] On 18 December 2008 Müller's doctor declared him no longer fit to play, as his condition grew worse.

[4] After Müller's death it was announced that the Kölner Haie, Adler Mannheim, and EHC Klostersee would all retire his number 80.