Attracting attention has always been normal for Niamh McKevitt in her football career. At 16, she is the captain of the South Yorkshire Girls under 17s squad, has represented the Republic of Ireland Women at junior international level, and started playing for Huddersfield Town in the FA Women’s Premier League while still at school. But it’s not her accomplishments in the women’s game that make her stand out. It’s this: since she was 12, Niamh has been the only girl in England playing football in the boys’ leagues, and she’s now written about her experiences in a book called Playing With the Boys.

“If you haven't played the team before, what happens is they'll be doing the warm-up and a ripple goes through the team,” she explains when I ask how boys react to seeing a girl on the opposition. “One will notice there's a girl, then another, then another, then another, and then suddenly they'll all stop their warm-up and are staring over in shock, like, ‘Oh my gosh!’”

The eyeballing hasn’t deterred her. In fact, with the support of her dad Steve, she has directly contributed to the FA progressively changing its rules on mixed football until this year, when the age limit was raised to under 18s.

Asked whether she’s encountered much hostility during her incursions on the boys’ game, McKevitt tends to talk it down: “I wouldn't say there's been any flat-out, very awful sexism.”

This is generous, considering that she describes being catcalled and called a “slag” by her male opponents – although she’s always felt that, once the novelty of her sex has worn off, her teammates have accepted her on her abilities. But compare her experiences to those of a typical boy starting out in football, and it’s obvious that she’s had to scrap from the very start. As a five-year-old, she would constantly be picked last for teams – even being passed over at one point in favour of a four-year-old boy who could barely kick the ball.

And it wasn’t just her peers who doubted that she belonged in the game. Although McKevitt has had several outstanding coaches, some of the adults who should have been supporting her preferred instead to be downright obstructive. In the book, she writes about how, aged ten and already an accomplished player in Sheffield Wednesday boys’ academy, she tried out for the school football team. The coach hired by the school immediately tried to rule her out of consideration as a “non-player”, then the school blamed spurious “insurance reasons” for her exclusion, and finally started a girls’ team rather than let her play mixed football. “They didn’t think it was fair that a boy should miss out on a place because of me,” McKevitt writes, with an admirable lack of bitterness.

It’s one of the perversities of sexism that, by excluding women (or in this case, girls) from consideration, it ensures that a role will go to a man (or boy) who just isn’t as good. Janet Radcliffe Richards dissects this in her book The Sceptical Feminist as follows:

“What… must be happening if an employer passes over a competent woman in favour of a less competent man? It means the job will be less well done, and therefore… that he will be losing money [or football games] by appointing the man. Why should he do that? He is actually willing to pay for something or other, and it is hard to see what it could possibly be other than the simple cause of male supremacy.”

For over a decade, McKevitt has been quietly forcing opponents and spectators to give up on the idea of her inferiority. However, there is one objection to her playing in the boys’ leagues besides the sexist one that she just shouldn’t be taking a place of a boy, and it’s this: wouldn’t it be better for all girls if a player of McKevitt’s ability stayed within the girls' game and improved it from the inside?

But, as with McKevitt’s primary school team, the girls’ game is far too often an afterthought. Under-resourced, patronised by the media if it’s noticed at all, and without the kind of scouting structure that ensures skilled boys are helped to find their level, the girls’ game simply isn’t able to foster talent in the same way.

“There are girls who've gone through the all-girls' system and come out as the great players they are,” says McKevitt. “But personally, I don't think I would have achieved what I have in football if I hadn't played with the boys.”

As a right-back who takes obvious pleasure in tackling (she writes repeatedly about how much she enjoys winning 50-50 balls, and occasionally clattering her man in the process), playing boys meant she always had to deal with an opponent who could match her physically – which meant she had to keep on getting better when she could perhaps have coasted on her strength and speed in less competitive girls’ grassroots football.

However, although the rising age limit imposed by the FA shows that a hard boundary on mixed football makes little sense, it’s true that the physical differences between girls and boys eventually start to tell – though this isn’t necessarily to the detriment of the women’s game.

“I think technically the women's league is better,” says McKevitt. “[Women] don't have the leg strength for 60-yard passes over the top, and they don't have as much muscle so they don't have that kind of explosive speed where you go from a standing start to flat out sprinting. That's a lot rarer in the women's game. So there's a lot more passing and I find it a lot more tactical.”

Being a pioneer is peculiarly demanding. For McKevitt, overcoming other people's underestimation of her has meant she’s always had to overachieve somewhat. "Good enough" is never good enough when you’re the only girl in the league:

“What happens is, if a boy in my team was playing badly, he was playing badly because he was having a bad game. If a boy got kicked in the face and cried, it was because he got kicked in the face and it hurt. If I was playing badly, I was playing badly because girls can't play football. If I got kicked in the face and cried, it was because girls can't play football.”

But with more girls coming up behind her (McKevitt says there are now 76 girls registered in her former league), the burden of being the exception is getting lighter for each cohort. The future of women’s football could be in the boys’ game.