In 2005, when Landon Donovan expressed his desire to return to MLS, the Galaxy traded Ruiz to FC Dallas for the #1 allocation in the MLS pecking order, so that they could acquire Donovan. Ruiz finished his first year in Dallas with 11 goals and two assists. During the postseason in the conference semifinals, Ruiz scored two goals in the second leg match against the Colorado Rapids, but FC Dallas were eliminated on penalty kicks. In February 2006, MLS fully bought Ruiz's contract rights from his former club, Municipal, and FC Dallas was able to negotiate a multi-year deal. In March 2006, a bicycle kick goal he scored against D.C. United was selected as the "Goal of the Decade" in MLS through online voting.