After his junior year, Arnaud turned professional, and was drafted 50th overall in the 2002 MLS SuperDraft by the Kansas City Wizards. He hardly played at all his first year, registering only 43 minutes in three games. Although his second year began much the same, Arnaud began to get significant time as the year progressed, and finished the year having played in 18 games, and scored three goals. Although his performance in 2003 boded well for his 2004 season, Arnaud exceeded everybody's expectations. After Preki and Igor Simutenkov went down with long-term injuries before the beginning of the season, Arnaud was given a starting role in the Wizards' offense next to Josh Wolff. Arnaud proved he deserved the opportunity from the outset, and went on to start all 30 of Kansas City's games, scoring nine goals and eight assists while leading the club to first place in the Western Conference.