He will now join forces with brothers David and Mike in the senior set-up with the Gunners - and fly-half Alex insists he can push his siblings all the way for places with both club and country.
"If I hadn't got a contract now I'd be going into a third year in the academy and I feel I need to be pushed now," said Blair.
"I've maybe been in a bit of comfort zone, so this will hopefully bring the challenge I need.
"I'm very keen to play stand-off. I've played there from a very young age and played centre a lot as well, and Rob (Moffat) likes the fact I am a stand-off but can play other positions.
"There is a balance because it can be good learning things about other positions, but I want to play the main extent of my rugby at ten and stick at one position.
"We are all very close, and it will be challenging and competitive, and good fun. I don't think anything will come between us, though, because we're close."