While Adu's early play in MLS didn't meet rise to phenom
heights, he did create a spike in attendance for D.C. United road games during his first season.
Adu, who scored had 11 goals and 17 assists in 87 regular-season games for D.C. United, will reunite in Salt Lake City with head coach John Ellinger, who was Adu's U.S. U-17 national team coach.
Adu gave one of his best performances in the 2006 semifinal against New England, but was subbed by Coach Peter Nowak in the 65th minute of the 1-0 loss.
In 2005, Nowak suspended Adu for a playoff game for complaining about a lack of playing time.
"It was not an easy decision," United President Kevin Payne told the Washington Post. "Freddy has been an important part of our team, but we saw an opportunity to do something for both him and for the future of our team.
"Freddy wanted to play central midfield or withdrawn forward. On our team, that's Christian Gomez and Jaime Moreno and that wasn't likely to happen."