He played for 16 seasons as a forward, finishing his career with Columbus Crew SC, before turning to coaching with his former club Colorado Rapids.

[1] After playing well in the 2000 Summer Olympics Casey signed a four-year contract with German club Borussia Dortmund.

After finishing a year of playing with the club, Casey was loaned out in the 2001–02 season to Hannover 96, where he scored seven goals in nineteen games.

[7] On December 14, 2012, Casey was selected by Philadelphia Union in the first round of the 2012 MLS Re-Entry Draft, Stage 2.

[10] Casey played at the 2001 World Youth Championship in Argentina and then graduated to the senior United States national team, getting his first cap on March 31, 2004, against Poland.

On July 7, 2005, Casey suffered a tear to his ACL while playing against Cuba in the U.S.'s opening game of the Gold Cup.

[14] Charleston and Casey mutually agreed to part ways on October 12, 2022, before the final match of the season after a dismal year of only six wins in 33 contests.