He was selected third overall in the 2004 NHL Entry Draft by the Chicago Blackhawks and spent four seasons with the club before being traded to the Minnesota Wild in 2010.

As WHL champions, they earned a berth in the 2004 Memorial Cup, however, Medicine Hat was defeated by the Gatineau Olympiques in the semi-final.

As such, the NHLPA argued that Barker (as well as five other Blackhawks players in the same situation) qualified as an unrestricted free agent and could entertain offers from other teams around the league.

[11] Given salary cap constraints caused by having to overpay Barker and others, he was traded on February 12, 2010, to the Minnesota Wild for defenceman Kim Johnsson and defensive prospect Nick Leddy.

[citation needed] In September 2012, Barker was invited to the AHL's Texas Stars training camp and later made it to the main roster.

Barker marked his first return to the AHL since 2008 by debuting for the Stars to start the 2012–13 season, on October 13 in a game against San Antonio Rampage.

[citation needed] On November 5, 2013, Barker signed a one-year deal with Barys Astana of the Kontinental Hockey League (KHL).

[17] After spending the 2013–14 season in the KHL, Barker returned to North America and attended training camp with the Blackhawks on a player tryout offer.

[21] After another shortened stint with Slovan Bratislava, Barker left the KHL and signed with the SCL Tigers of the Swiss National League (NL) on January 12, 2018, until the end of the 2017-18 season.

[23] After spending his last two professional seasons in France with the Dragons de Rouen of the Ligue Magnus, Barker ended his 15-year playing career by retiring and accepting an assistant coaching role with a junior Canadian club, the Penticton Vees of the British Columbia Hockey League (BCHL), on June 23, 2021.