The Harrogate squash player has spent 15 years at the top of the game, travelling the world and representing England more than 100 times in the process.
But earlier this year, she felt the time was right to open up about her romantic relationship with Australian player Rachael Grinham, one which has put their professional rivalry to the test.
The couple announced their relationship in an interview with the US Squash Magazine in May and by doing so, they became the first openly gay squash players, competing against each other.
It was a revelation that broke new ground for a sport already far ahead of its peers in its attitude towards equal prize money, but one that was no surprise for Duncalf’s inner circle of friends and family, nor wider throughout the rest of her sport.
“There was no revelation for me, my friends or my family – most people knew,” Duncalf told The Yorkshire Post.
“I would never have done it five years ago but I thought if it can help anyone else then it’s worth it. I’m not a big trailblazer of gay people, but I am glad I have done it.
“I got a lot of messages from people I went to school with or people that are outside of squash, saying: ‘you’re so brave’. I didn’t feel brave, but it was nice to hear people say that it was inspiring.
“For me it wasn’t a massive big deal. Everyone in my circle has known about me and Rach for ages. It is an interesting dynamic that we actually compete against each other. That’s quite rare.”
Indeed, such competition has thrown up its own challenges for Duncalf and Grinham, 40.
Despite Duncalf’s move to Brisbane in 2015, the couple have strayed away from training alongside each other because of the 34-year-old’s tendency to over-compete. Matches between them have been few and far between in recent years although Duncalf, the former world No 2, beat Grinham to win her only major squash title at the Qatar Classic in 2009.
“She is much better at losing than I am, so it helps if I win,” joked Duncalf.
“We don’t train together that much. I behave badly with Rach, it’s like that when you are so close to someone. I was always like that with my brother.
“In a match, it’s always been totally fine. It’s always going to be a fair match and at least one of us will get through.
“But I am not a good loser, I will need an hour or so to stop sulking whereas she is much better. I’m far more competitive than Rach is.”
Duncalf’s competitive spirit has been tested in recent years after sliding down the world rankings from second only to legendary player Nicol David to her current ranking of 30.
But she has been forced to rein in her on-court emotions since she took on the responsibly of women’s president of the Professional Squash Association.
It is a role that has seen her take a leading stance on pay equality across its world tour, with events spread wide from Doha to Hong Kong and Grand Central Station in New York.
As a non-Olympic sport, the strength of tour events are paramount to the well-being and financial stability of players – a thing that has challenged Duncalf with her rankings slide and move to Australia.
Duncalf, who has been capped more than 100 times for England, said: “I am involved as much as I want to be – board meetings, decision making – anything and everything to do with the tour.
“As president, I have had to think more about some things. I’m not irresponsible but I have to be a bit more organised and set a good example to the other players. As a 34-year-old I am one of the older players on the tour. I did it to look after the other players at board level and make sure they are represented.
“We have achieved a lot in terms of equal prize money. It has been a huge thing, I am proud of that. We are just trying to make the sport a decent spectacle and a well-oiled machine that can be marketed. It’s not easy being a minority sport, even if you’re a successful one. But we want to help keep the sport going, and it is.”
The Olympic debate remains the elephant in the room for most squash players.
Squash’s continued exclusion as part of the Olympic family has puzzled most in the sport – and many out of it.
Ahead of the 2016 Olympics, the racquet sport missed out on inclusion behind golf and rugby sevens and despite hope being raised ahead of Tokyo 2020, it was rebuffed once more by the International Olympic Committee as baseball/softball, karate, skateboarding, sports climbing and surfing clinched a place.
Squash’s dreams of joining them for a future spectacle have been boosted by an inclusion to the 2018 Youth Olympics.
But now, an emerging threat has appeared from outside the box – or, more so, inside it.
Murmurings are beginning to surface that the eSports movement – competitive computer gaming – could be a genuine rival for inclusion for Paris 2024 or Los Angeles 2028, a sickening suggestion for Duncalf and her peers.
“For me, I would give anything for squash to be in the Olympics. But when they’re talking about computer gaming being in it, you just laugh,” Duncalf added.
“It’s a joke that we’re not in it and it’s very frustrating for any squash player. We have a great sport and a successful tour. One day I would love to see squash in the Olympics, but the way the IOC operate and what you see, you just don’t know.
“They tell you things like that it has to be geographically around the world. It’s a load of rubbish. Squash ticks every box but we aren’t in it. I have got my hopes up so many times before and it hasn’t happened.
“Of course you are angry, when you see other sports, surfing, it’s ridiculous. Squash is one of the hardest sports out there. The Olympics is supposed to be about sporting events. But they just dismiss us every time.”
The Commonwealth Games remains squash’s showpiece in a multi-sport event and Duncalf’s permanent move to Australia has given her an insight into the build-up for the spectacle at the Gold Coast early next year.
Having won silver at the World Doubles Championships alongside Alison Waters this summer, the Harrogate player is hopeful she will earn a call-up to a fourth Commonwealths, where she will bid to add to silver medals won in 2010 and 2014.
Duncalf, who is now coached by 1991 world champion Rodny Martin in Australia, added: “I have played three Commonwealth Games already and I look forward to them.
“It’s a special chance to be part of such a big team in a multi-sport event. Some of my favourite memories are from the Commonwealths.
“The Gold Coast will be pretty good. There’s already loads of hype. They are all excited for it.”