Having won six games on the trot for the first time in Brad Scott's coaching tenure, the Kangaroos will make the journey to Sydney to face the Swans in Friday night's preliminary final brimming with confidence.
A spot in the Grand Final awaits the Kangaroos if they can cause a gigantic upset, a far cry from the team that was battling to validate its finals credentials at the midway point of the season.
"Those losses earlier in the year were a reflection of where we were at then and probably why we finished sixth (on the ladder) and no higher," Petrie told AFL.com.au on Sunday.
"We've proven now that we are a top-four side. We left our run late and it was important to prove to our supporters that we are capable of winning finals.
"The jury was out up until two weeks ago, but we're now a genuine contender to be there on the last Saturday in September."
Inconsistency plagued the Roos earlier in the season and the team lost games a side with finals aspirations really should have won.
"I think we've ironed a lot of those kinks out. We were tweaking our game-plan at certain times throughout the year and guys weren't following instructions to the letter," Petrie said.
"But in the last six weeks – and especially the last two weeks – you've seen how good we are when we are following team rules."
Despite overcoming Geelong in Friday night's semi-final, North will head into the clash with the Swans as clear underdogs.
However, the Kangaroos can take heart that they were one of only five sides (Greater Western Sydney, Collingwood, Hawthorn and Richmond were the others) to beat the Swans this year.
The Roos recorded a comprehensive 43-point victory when the sides met in round four.
"We're confident we can win anywhere," Petrie said.
"It's going to be the toughest game we've played for the year but given how well we've played over the last two weeks we're capable of beating them."
