[2] Though considered an adequate right back, Gargan was waived by the Rapids early in the 2008 season, after undergoing surgery for both a torn ACL and separated shoulder that offseason, as they faced a roster crunch and a surplus of defenders.

Following a brief period as an unattached player on trial, Gargan was signed by Chivas USA on April 25, 2008.,[2] but announced his retirement from professional soccer, citing personal reasons, on May 9, 2008, without playing a game.

Less than a month after joining Chicago from Toronto, Gargan started his third match for the Fire against his old side and tallied a 69th-minute header off a cross from Pavel Pardo to help his new club to a 2–0 victory on August 21, 2011.

Gargan would appear in a total of nine league matches to close out the 2011 campaign and an additional two in the Lamar Hunt U.S. Open Cup, helping the team back to its first final since 2006, where they eventually fell 2–0 to Seattle Sounders F.C.

On December 14, 2012, after a new contract was unable to be agreed upon, he was selected as the ninth pick in the 2012 MLS Re-Entry Draft by San Jose Earthquakes.

[10] Gargan and the LA Galaxy were forced to part ways on February 29, 2016, as a result of salary cap considerations a few days prior to the start of the 2016 and roster compliance.