Kerr, 21, underwent a reconstruction of her left knee when she was 17 and then last December she sustained a further injury to the same knee playing for Perth Glory in a W-League match.

The fact the World Cup was only six months away at the time naturally made her nervous about how the injury might affect her chances of making the squad, but she recovered as well as could be expected and flew out of Sydney with the rest of the Matildas on Saturday.

Kerr comes across as very mature and determined for one still so young, which is no doubt largely the result of what she has been through and the lessons she has learned in handling those injury issues.

"I had a reconstruction previously, but this time I hurt the cartilage in my knee," Kerr told The World Game.

"It's called a chondral defect. It's pretty much a hole in the cartilage and I had to get it fixed up and it's been difficult, but it's come good now.

"The doctors think maybe there was some connection, but not directly, from the ACL injury.

"What they did with the new injury was try to regenerate cartilage growth. They gave me a micro fracture in the knee - they drilled holes in the knee and broke it a little bit to cause trauma, and then it bleeds and they try to regenerate cartilage that way.

"It's like a trick of the brain. They try to trick the brain and fix something else in the meantime. It's pretty hard to explain - I don't know too much about it in-depth."

Being immobile over the summer, at a time when the W-League season was ending and Kerr would have obviously been planning on being injury-free and looking towards the World Cup, was very frustrating for her.

"I had the operation on December 16," she said. "I was in hospital for two days and then on crutches for seven weeks. I wasn't allowed any weight-bearing for that seven-week period, which was probably the toughest part of the injury.

"It was pretty irritating over the Christmas-New Year break. It was really difficult over that period.

"It was in the back of my mind that the World Cup wasn't far away. It was definitely the first thing I thought about when I got hurt, but the medical staff assured me straight away that I'd be back in time and that made me feel a bit better about it.

"I feel pretty lucky that I'm playing again now and ready to go in the tournament."

Asked to describe the effect having to deal with major injuries at a young age has had on her, Kerr replied: "It has made me tougher and also made me grow up a lot.

"When you're young you kind of think you're invincible and when things like this happen now I know how to react to it and I can support other people through it as well, if it happens to them.

"It's obviously not the nicest thing to have to go through, but it's more mentally difficult than anything else. It has made me stronger mentally.

"A lot of people say that sometimes a setback can make you stronger and it has, with me.

"I've grown as a person and I know that just doing all of the training isn't good enough these days, I've got to take care of my body on and off the field and be professional about how I act and what I do."

Kerr is one of the major attacking options for the Matildas. She scored two goals as the team walloped Vietnam 11-0 in its farewell match in Sydney on Thursday.

Alen Stajcic is the coach who will steer the Matildas through the World Cup campaign and Kerr said his influence on the squad had been hugely positive.

"We've had a lot of change," she said. "Obviously every new coach brings in change, and we're really positive about what 'Staj' is doing.

"I think the players have got this inner confidence in each other now that we've never really had before.

"Everyone is really believing in the system and we've become a tighter group on and off the field and that builds success.

"You've got to be like a family in a squad like this and that's what we're trying to create. It doesn't change totally over a few months, but the process has begun and the World Cup is a good place for us to see what effect it can have on the field.

"It's the world stage, the biggest event in women's football, and everyone in the squad is very excited to be taking part. It's going to be massive."