With the acclaimed new football documentary Next Goal Wins now showing at the IFI in Dublin, John Byrne talks to stars Thomas Rongen and Jaiyah Saelua.

Next Goal Wins (review: http://bit.ly/1m1Cmyo) is one of the most uplifting documentaries ever made. But the fact that it's about sport is merely incidental.

Filmed in American Samoa – a small cluster of islands in the South Pacific – it tells the story of the national football team as it struggles to overcome its tag as the world's worst team.

Things begin to change when a Dutch coach, Thomas Rongen, arrives. A 50-something with plenty of experience in the US, he encourages his squad of amateurs to improve themselves, while seeking out qualified players who may be off-radar elsewhere.

Amongst his squad is Jaiyah Saelua, a player who belongs to American Samoa's third gender, Fa'afafine (Way of the Woman). Jaiyah becomes the first transgender person to play in a World Cup qualifier – but more importantly, represents the inclusivity that prevails in American Samoan society.

She's regarded as just another member of the squad, and in Next Goal Wins is as likely to be seen crimping her hair in the dressing-room as making hair-raising tackles on the pitch.

Over in London to promote Next Goal Wins, Thomas Rongen and Jaiyah Saelua seem genuinely thrilled at the general response to the film.

Thomas Rongen (TR) It really is as pure as you see it. It's factual. It plays out in front of your eyes. It's the underdog story but it's more than just a footballing winners/losers story: it's about humanity, it's about people. It's about rekindling the love of the game, the passion when we all started playing this game when we were young. It's about religion and inclusivity, and not judging people on race, gender, sexuality, whatever it might be.

Jaiyah Saelua (JS) You can learn from the people and the culture, and the traditions and the values. Coach Thomas obviously learned a lot, and in turn we were hungry to learn also from him. We took the opportunity to learn from someone who truly cared about us developing as players.

John Byrne (JB) Your journey is amazing and inspirational.

JS Thank you. I think, not only my story, but I think the world can also learn lessons from the boys and the culture, and how important it is to include everyone. It's a sport that's too beautiful to include discrimination and hate. It should be available to everyone, no matter [what] their background is.

JB It must have been a privilege to be the first transgender player to play in a World Cup qualifier.

JS It's a big honour and I'm very proud that I'm able to die now! I take pride in knowing that not too many people will get to be called the first in the world or be the only one in the world.

JB Ultimately, isn't this is a story about the positive side of the human spirit?

TR It's made me a better person – and a better manager. I'm so happy that I was part of something really special. It's just beautiful. It's a football story but it's a lot more. It's real life. It's pure. It's holistic. It's a bunch of amateurs that play because they love the game. And we don't see that anymore at the highest level in the West.

I think that's a very important message that this movie sends out. It talks about love in different ways: loving the game, loving each other, loving family. Respecting opponents, respecting yourself – those are all underlying themes that we weren't aware of while going through this journey. This movie encapsulates all that very, very well.

At the end, it's still about the underdog, about doing something very special. A loser becomes a winner, which everyone wants to root for. It's a must-see movie in my opinion.