The 22-year-old Scot had been expecting to be on Edinburgh Accies duty at this early stage of the season.
However his elevation to Andy Robinson's professional side has been a success so far and the former England coach will keep faith with Blair for the European match at Murrayfield.
Blair moved north after a spell with Sale Sharks but was ready to bide his time before playing the big matches for Edinburgh alongside brother Mike Blair.
The chance to face Stade Toulouse comes after he impressed in the Magners League.
And he said: "I'm looking forward to it. This is my first Heineken Cup game and this is what you play for; playing against one of the biggest teams, so you can see where you're at.
"I think we lost by a couple of points at Stirling County and I didn't really think I would be playing against Toulouse in the Heineken Cup when I last lined up for Accies.
"At that point, I didn't even think I was that close to playing in the Magners League, but it is a nice feeling.
"I've just been waiting for an opportunity.
"At Sale, it was frustrating because I didn't get a lot of backing and when I did I got injured.
"Now it is nice to be given three games in a row. It is good in that respect that I'm getting continuity and that I can show what to do."
He will have a surprise chance to come up against former Sale colleague Valentin Courrent, who is set to line up as Blair's opposite number.
Blair said: "Valentin was at Sale when I was there. He is playing at 10 as well on Saturday, so that will be good fun to play against him because I got to know him quite well.
"We were in a similar situation because we were both away from home and we were both going for the same position. It should be interesting and it will be good to see him again."