He joined Basel's first team for their 2000–01 season under head coach Christian Gross. Because Gross had other good strikers such as Jean-Michel Tchouga, Edmond N'Tiamoah, Hervé Tum and George Koumantarakis, he used Muff as a winger. After playing in five test games Muff played his domestic league debut for the club in the away game on 19 July 2000 as Basel were defeated 2–0 by Xamax.
He joined Basel's first team during their 2000-2001 season under coach Christian Gross.  Gross had other strong strikers like Jean-Michel Tchouga, Edmond N'Tiamoah, Hervé Tum, and George Koumantarakis, so he used Muff as a winger. After playing in five practice matches, Muff made his official debut for the club in an away game against Xamax on July 19, 2000, where Basel lost 2-0.