The forward from Thunder Bay, Ont., hadn't played for Canada in a world championship or Four Nations Cup when she was summoned to try out for the 2010 Olympic women's squad.
Irwin turned that out-of-the-blue invitation into a spot on the team and an Olympic gold medal in Vancouver.
"It was a phone call unexpected on my part and everyone else's," Irwin recalled Tuesday in Calgary. "The door was open and I made sure I opened it all the way.
"In the end, I think they just saw that grit and determination I played with. I think I consistently brought that element to my game."
There are 40 players at a national team camp in Calgary this week wanting to impress Olympic coach Dan Church and head scout Melody Davidson.
They must continue to impress when they return to their respective club or university teams this winter if they want to play for a gold medal in Sochi, Russia, in 2014. Church plans to invite 29 or 30 to try out for his Olympic team.
"These are the ones who have a realistic chance of being in that group," Church said. "They're being evaluated. This week is the first step to that path."
Hockey Canada's practice has been to bring the women together in Calgary for half a year prior to the Winter Games to both train the team and whittle the roster down to the chosen squad. So by this time next year, the 2014 team's preparation will be in full swing.
Church and Davidson will likely announce simultaneously both the world championship roster and the group of players invited to Calgary, just prior to the 2013 women's world championship April 2-9 in Ottawa.
Church, the head coach of the York University women's team, will be behind Canada's bench in Ottawa and also through the 2013-14 centralized period in Calgary.
The difference in the women's preparation for Sochi is they'll train out of the new Winter Sport Institute at Calgary's Canada Olympic Park, which is also the site of the team's camp this week.
Hockey Canada moved its headquarters there last year. The women will have access to an Olympic-sized ice surface, a spacious dressing room, dryland training facilities and sports medicine and nutrition as they gear up for Sochi.
It's a hockey environment fit for a professional men's team. For the women experiencing the posh new facility for the first time at this week's camp, it's extra incentive this winter.
"This is an incredible facility. The resources here are endless," said defenceman Bobbi-Jo Slusar of Swift Current, Sask.
"It's luxury here. It's that privilege and you earn that, so when you get here, it feels really special to be a part of it, to be in the Hockey Canada dressing room. Everything is high-tech, state-of-the-art."
The players at camp this week are a mix of established veterans such as captain Hayley Wickenheiser, Jayna Hefford, Gillian Apps and Caroline Ouellette alongside talent coming out of the under-22 and under-18 teams.
Defenceman Erin Ambrose of Keswick, Ont., was captain of the Canadian team that won gold at this year's world under-18 championship.
"This camp will see how I can do against this level of competition," Ambrose said. "I need to continue to mature physically.
"That's one of the big steps I'm going to have to take. I'm not a big girl to begin with. Some of the girls have quite a few years of training on me."
The women will play intra-squad games and four games against midget triple-A men's teams before camp concludes Saturday.
A regular schedule of games against Alberta Midget Hockey League teams was key in the women's gold medals at both the 2006 and 2010 Winter Games.
"The midget league is so important in our preparation," Church said. "They've been phenomenal partners. As far as I know, that relationship is going to continue and that's critical."
The Four Nations Cup in Finland in November, the under-22 women's Meco Cup in January and one more national team camp in late January offer the few remaining chances for players to distinguish themselves prior to the announcement of the world championship and Olympic centralized rosters.
But Davidson will also scout them with their CIS, NCAA and CWHL teams this winter. Wickenheiser, who will play in her fifth Olympics in Sochi, says that's where players can really demonstrate their worthiness for the Olympic team.
"It's never what you do at a camp that really matters," Wickenheiser explained. "It's everything that you do before you get to camp and after you leave, when nobody's watching - that hard work and the habits.
"It comes down to doing the little things well all the time and being consistent. That separates players from the ones who will be there from the ones that won't."
Added Davidson: "The biggest thing we're looking for at every position is consistency of performance, consistency of habits, the intensity. It doesn't matter if you're at our camp or playing on your club team."