Dempsey was drafted ninth in the 2004 MLS SuperDraft by the New England Revolution after three seasons with Furman University. Playing all over the field, he scored seven goals in his rookie season, and was named MLS Rookie of the Year, despite missing a lot of time due to injury. In the playoffs, he missed the decisive penalty kick in a shootout against D.C. United that helped deny the Revs a trip to the MLS Cup.