On 24 November 2010, Nyassi was selected by Vancouver Whitecaps FC as their first pick in the 2010 MLS Expansion Draft[3] but he was immediately traded to Colorado Rapids for an international roster slot.

[4] On 20 July in a match versus New York Red Bulls, Nyassi scored his first MLS hat-trick and his first three goals for Colorado.

Strike partner Omar Cummings set up Nyassi with a lovely through ball and the Gambian scored with a curling shot to put his side 2–0 up.

[6] Nyassi spent 2 1/2 seasons with Montreal before being traded to Chicago Fire on 29 July 2014 in exchange for midfielder Dilly Duka.

He earned three caps playing for the Gambian U-17 national team in the 2005 African Under-17 Championship, scoring one goal against Burkina Faso.