The club agreed to carry out the investigation at the request of Cusack's family, after the 27-year-old died at her home in Derbyshire on 20 September.

Just before her death, Cusack had started her sixth season with the Blades in the Women's Championship and was the longest-serving player in their squad, with over 100 appearances. She also worked as a marketing executive at the club.

• Sheff Utd midfielder Maddy Cusack dies aged 27
• Police: No suspicious circumstances regarding Cusack death

Derbyshire Police said there were no suspicious circumstances surrounding her death. Last month, a coroner opened and adjourned an inquest into her death, local media reported.

On Monday, the Maddy Cusack Foundation, launched by the footballer's family, shared a speech on social media attributed to Cusack's mother, Deborah.

The statement was originally delivered at a memorial service for the former Blades vice-captain in late October.

In it, her mother said Cusack's "happy-go-lucky" spirit had gradually changed after February, and the reason she was speaking at the memorial was because of football.

"From February this year, the indomitable, irrepressible spirit, the spirit called Maddy, the spirit that I had so fearlessly protected was allowed to be broken. Taking her away from me," the statement read.

"Those who knew Maddy well will be aware that she had no long-standing mental health issues or troubles. Not that there would be anything to be ashamed of if there were, but there were not. Those that didn't know her need to know that.

"Maddy was a happy-go-lucky, carefree girl with everything to live for and by last Christmas could be described as being at her happiest. This all changed gradually from February this year."

The statement continued: "Sheffield United Football Club have agreed at the request of Maddy's family to carry out a thorough external investigation into the events that her family believe contributed significantly to her passing at the tender age of 27."

It said the investigation is "no secret, nor should it be".

The social media post, which was later modified, was met with support from Sheffield United former goalkeeper Nina Wilson, who shared the statement saying: "Very important read, time to do better football. She won't be forgotten."

Lucy Watson, who joined Chelsea from Sheffield United last summer, added: "Never going to stop loving you Mads," when sharing the post to her story on Instagram.

Sheffield United FC declined to comment.