She should have been part of Scotland’s lineup against Wales this afternoon, Instead Siobhan Cattigan’s parents are mourning a daughter lost to them, they believe, because of the head injuries she sustained as a player.

When Scotland meets Wales in today’s feature game of the World Cup, one lifetime rugby fan’s thoughts will turn not to the 30 women who will take the field to start the match, but one that isn’t.

Neil Cattigan’s daughter Siobhan, a Scotland back-rower, died suddenly in September last year. He believes the 26-year-old’s death was the direct result of head injuries suffered while playing rugby and, more pointedly, the failure to manage the after-effects of these injuries properly.

The anger and sorrow as he talks about Siobhan’s final weeks and days is palpable, even on the phone from Scotland, where he and wife Morven live and mourn.

“It’s very difficult,” he says, breaking down as he tries to get the words out. “She should be there. If due diligence had been carried out, she would be.”

The harrowing final months of Siobhan’s life were covered poignantly in the Sunday Times, but whereas the Scotland team that meets Wales tomorrow has been able to pick up the pieces and move on, Neil Cattigan cannot.

While limited to what he can say as he has filed a lawsuit against World Rugby and the Scottish Rugby Union (SRU) for what they claim is failure to follow head injury protocols, Cattigan is still haunted by what he describes as his own failures.

“I’m a father. My main job as a father is to protect my family. I failed.”

He said the lawsuit is not about money – any funds would go towards a foundation in Siobhan’s name – but to get to the truth about why the SRU failed in their duty of care.

“They fixed her broken bones but turned their backs on her broken brain,” Cattigan says. “She was so badly let down. The protocols are not fit for purpose; concussion affects females entirely differently from males so the protocols need to change before anyone else suffers.”

Cattigan claims it was not until six weeks had passed after Siobhan died that they learned about the link between concussions, “head knocks” and sub-concussions causing neurological damage.

“We are in no doubt led to the decline in Siobhan’s physical and mental wellbeing. We didn’t know because we believe the data and research has been deliberately suppressed,” Cattigan says.

“She has been playing rugby since she was six, has suffered several concussions playing for Scotland,  but it’s only recently that I have learned about the dangers also of sub-concussions; that females generally take 30 percent longer to recover and that their necks are 28% weaker; and that females make up only eight percent of concussion data.

“The difficulty is trying to get people to be honest with us – that includes doctors, coaches and rugby’s hierarchy – to help us understand what happened to Siobhan, which is truly devastating.

“They messed up with Siobhan. They got it wrong.”

In the time before she passed, they say, it became obvious that Siobhan’s brain was broken.

Cattigan said: “She had gone from loving life, being full of fun and joy with everything to live for, as she repeatedly said, to being broken because she didn’t know what she was dealing with. It terrified her.”

The Cattigans say their daughter succumbed to an impulse because her brain had changed. Mum Morven told the Sunday Times that  the only thing she could compare Siobhan’s decline to was dementia patients.

“I couldn’t think of anything that would change a personality so massively, something that completely alters you as a person. Siobhan was crumbling before our eyes and something catastrophic had happened in her brain.”

The change in personality and outlook was rapid and, Neil Cattigan says, the treatment she received was mere lip service.

What the family do not want is for their daughter to be forgotten or, as Cattigan puts it, edited out of history.

It feels like the SRU have tried to erase Siobhan again. She was not mentioned in their “Road to NZ” promotion despite her having played a big part in getting the team to where they are.

In part to redress that, The family have launched the #rememberSiobhan hashtag, which has already garnered some high-profile shares on social media from former All Blacks and Black Ferns.

SRU did not respond to this story for comment about how they intended marking Siobhan’s contribution and death while at the World Cup. They did release a statement in August when her story first got global attention, addressing some of the Cattigans’ concerns.

“We fully acknowledge the seriousness of what the family [has] shared. However, there are details and assertions about how our people are said to have acted that we do not recognise or accept. Respecting medical confidentiality, and with reference [to the legal claim], we are not in a position to communicate further on any details of Siobhan’s care at this time.”

In the statement SRU said their offer of support for the family “remained open”, but the Cattigans described the national body’s response to their daughter’s death and the subsequent publicity as “a circus”.

They say that invitations to teammates to attend Siobhan’s funeral were not passed on and then there was the interview with head of Scotland’s players’ association Bill Mitchell, where he appeared to speak on behalf of the players when he said: “We cannot and will not challenge what the Cattigans believe [but] what we can do is put forward our understanding of how this squad experience playing for Scotland, and the support they receive … the healthcare they receive is excellent, the pastoral care is excellent, and they [the squad] are upset at the inference that can be drawn that it was less than that.”

Within hours, many Scotland players had released their own statement on Twitter, saying: “We were unaware of this… article being published,” it read, “or the statements attributed to the team in this article. We are grieving our friend and teammate, our thoughts are with Siobhan’s family.”

“It’s a circus, and we don’t want Siobhan to be part of a circus,” Neil Cattigan says. “She was so much more than that.”

For Cattigan, the World Cup is both a beautiful thing and a horrible reminder of what he has lost.

“Hopefully I won’t wake up tomorrow, but I probably will,” he says.