Cusiter was one of the surprise omissions from Frank Hadden's starting XV for Saturday's first autumn Test against Argentina.
The Aberdeen-born 23-year-old was one of the highlights of the Lions tour to New Zealand in the summer, making a name for himself in Sir Clive Woodward's midweek side despite failing to feature in the Test arena.
The Borders player has continued that form this season with Steve Bates' improving side at Netherdale, but has lost his international place for the first time in two seasons.
Hadden has kept faith with his former Edinburgh charge Blair after the 24-year-old played a starring role in the summer victories over the Barbarians and Romania when the coach was in temporary charge of the national team.
Cusiter is disappointed to be on the bench at Murrayfield this weekend but knows Blair perhaps deserves a run in the team.
He said: "Mike has had to sit on the sidelines for the last two seasons and watch me play, so he has his chance now. It is up to him to show what he can do.
"I just have to take my chance when it comes. If it's going to be in this game, the Six Nations or whenever, I've got to be ready to take it and that's what I'm concentrating on.
"I've probably now got an extra edge to get my place back as I've not been in this situation before.
"I've only been involved with Scotland for two seasons so far, this is my third, and I've started every game.
"It is a bit of a challenge for me and I'll use that as motivation when I do come on and play.
"I'm obviously disappointed and the reasons have been given by Frank that he wants to keep continuity going from the side that played in the summer.
"I'm disappointed as I feel as though I've been playing well this season."
Hadden's men are set to face a physical challenge from Argentina, but Cusiter cannot wait for the talking to stop.
He added: "The team are up for this Argentina game. There has been a good enthusiasm in the camp and we now just want to play.
"Hopefully we can go out and express ourselves."