Boss played college soccer for the University of Tulsa from 2000–2004, starting 20 games, and also featured for Cascade Surge, Vermont Voltage and Fort Wayne Fever in the USL Premier Development League.

In 2008 Boss returned to Charlotte and was the starting goalkeeper for a team that finished in first place in USL2, before losing in the league's title game to the Cleveland City Stars.

He made his MLS debut on April 22, 2010 in the Sounders' game against FC Dallas as a second-half substitute for an injured Kasey Keller.

Boss earned a shutout in his first international cap for Puerto Rico in a 1–0 victory over the Dominican Republic in a World Cup Qualifier in March 2008.

His brother, Kevin, won a Super Bowl championship as a tight end with the New York Giants and also played for the Oakland Raiders and Kansas City Chiefs.