The 30-year-old believes there’s no reason North can't inflict another loss on the minor premiers on Friday night and win their way into the Grand Final.
“We’ve got the confidence inside the four walls at Arden St that we’ve got what’s capable to win the game,” Firrito told the Herald Sun at the team’s recovery session.
“Sydney has been a great side for a long time and they have got stars on every line pretty much, so we will have to be at our best. But we are confident we can get the job done.
“There is belief in the group that our best is good enough, and we’ve proven that now, to do it on the big stage in a finals atmosphere twice (against Essendon and Geelong).
“That’s all you need — belief in the group — and we’ve got it.”
North became the first club in seven years to win through to a preliminary final from outside the top-four.
“Offensively we have been pretty good for a couple of years now and it was just the other end that we had to tighten up and it, as always, is a balancing act,” he said.
“But we feel like we have got it reasonably good now and when we have got 22 blokes who are contributing we are a hard team to play against.
“We need to bring that to the table against Sydney this week.”
Although the Roos held Lance Franklin goal-less last time they met in Round 4, it’s another encounter that still stings the club.
“We know what he has done to us before (kicked 13 goals in Round 10, 2012), but Scotty Thompson played on him last time and did a superb job,” he said.
“It was early in the year when we played them and they probably weren’t at their best, so we know it counts for nothing now.
“But we have taken a little bit of confidence out of it, all the same.”
On a personal level, the defender is pinching himself after contemplating retirement in 2013.
“It was awesome, it was just an amazing feeling,” he said.
“This is the time of the year you want to be playing in finals, and for a long time we haven’t been there.
“But to be at this stage of my career and to be in a prelim, well, they don’t come around too often, so we will be taking the opportunity with both hands.”
