In 1999, Walker spent his freshman season at the United States Air Force Academy where he was a member of the men's soccer team.

He played in ten of the Falcons' nineteen games, scoring three goals and adding one assist.

In February 2003, the San Jose Earthquakes selected Walker in the fourth round (thirty-ninth overall) of the 2003 MLS SuperDraft.

On July 9, 2008, the RailHawks traded Walker to the Rochester Rhinos in exchange for Hamed Diallo.

The Rhinos then immediately traded Walker and Chase Harrison to the Portland Timbers for Andrew Gregor.