Muller started his professional career in the 1992–93 season playing eleven games for HC Moscow Dynamo[3][4] of the Russian International Hockey League.
Muller represented several second- and third-division teams from Germany, including EHC Neuwied, Iserlohner EC, Bietigheim Steelers, Moskitos Essen, EV Ravensburg and EHF Passau Black Hawks.
[8] He then returned to Ravensburg,[9] where he had spent three years as a player, taking over as youth coach while also serving as assistant on the club's men's team in the second German division.
Prior to the 2015–16 season, Muller was appointed head coach of ESV Kaufbeuren, a member of Germany's second-tier DEL2.
[11] On February 16, 2016, Muller was fired by ESV Kaufbeuren after a series of two wins and 13 losses since the beginning of the new year.