Scotland will tackle the Oaks in Invercargill on Saturday and Barclay says the squad are desperate to impress from the first whistle.
He said: "The start is huge and I think the guys will come out of the blocks absolutely firing.
"We've trained for two and a half months now. Ultimately everything we've been doing from the gym to the running has been focusing on this one point.
"It's a huge game for us. We want to get off to a big start, it's important for us to do that, but we want to win the game first.
"You don't get second chances. You have to start well - that starts from the first game and you can break it down to the first few minutes of that game. We want to go out there and really get going."
Scotland scored six tries in a 42-0 rout of Romania in the 2007 tournament, but Barclay is refusing to be complacent.
He said: "It was four years ago. If you go in with that attitude you're going to come unstuck."
Barclay's personal performance at openside flanker will be key in securing quick possession which his team-mates can utilise.
He added: "Speed of ball is key for the game and my role is pretty important in that - getting to the rucks, being proactive, being aggressive and making sure we get quick ball for our backs.
"I think we've picked a back line, a back row and pack where if we get quick ball we can play exciting rugby."
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