Schwethelm began his professional career in 2005 with German side Köln 99ers (then called RheinEnergie Köln). He played sparingly for two seasons before seeing significant action starting with the 2007–08 season.[2] While with the 99ers, he participated in EuroCup 2005–06, 2006–07 Euroleague, and ULEB Cup 2007–08.
In 2009, the 99ers declared bankruptcy. Schwethelm was then linked to a two-year deal with fellow Bundesliga side Eisbären Bremerhaven.[3] In the 2009–10 season, he averaged a career-high seven points per game in helping the team to the league semifinals.[4]