He played at scrum-half for Glasgow Warriors, Newcastle Falcons, CA Brive and Edinburgh Rugby.

Blair spent most of his club career at Edinburgh, and was named in the Pro12 Dream team at the end of the 2007/08 season.

[2] Blair spent the 2012–13 season playing in France with Brive helping them to gain promotion back to the Top 14.

Blair was made captain of his country for the first time against Ireland in the 2008 Six Nations Championship and for the next 12 consecutive games.

At the 2008 Six Nations, he captained his squad to a 15–9 victory over England at Murrayfield to win the 2008 Calcutta Cup.

Having been left out of the original Lions touring squad to South Africa in 2009, Blair was called up as a replacement for the injured Tomás O'Leary on 11 May, starting against The Presidents XV and the Southern Kings and coming off the bench against the Sharks.

After finishing playing with Glasgow Warriors, Blair then became an assistant coach at the club, first under Gregor Townsend and then under Dave Rennie.

[4] For the 2023-24 season, he will once again team up with his former Glasgow Warriors boss Dave Rennie as assistant coach.