With an Olympic qualifier in the bag, the 400-metres hurdler was on track to achieve a big result Tokyo.

Having progressed to the semi-finals at the 2019 World Championships, Carli was eyeing a place in the final and potentially even a bid at an unlikely medal.

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Then her world came crashing down.

While training in the gym in February, Carli slipped and hit her head before a bar landed on her neck.

The Kembla Joggers athlete initially brushed off the incident as a concussion. Doctors, however, were more cautious and kept her in hospital for observation.

It's a decision that saved Carli's life.

While in hospital, she suffered a seizure, an event that prompted further testing.

Eventually she was diagnosed with a traumatic carotid artery dissection, essentially a tear in the primary vessel that provides blood to the brain.

It's an injury typically suffered in motor vehicle accidents, such is the force required to rupture the artery.

"Initially I just had symptoms consistent with concussion," Carli said. "I was lucky I had that seizure, the doctors said I would've died if I didn't have surgery.

"I was very unlucky to fall the way I did but I was also very lucky at the same time."

The surgery was a success, but her career was in tatters.

Forget about the Olympics, there was a chance Carli would never run again.

The one thing she had been working so hard towards had now been taken away from her.

"I cried, I just couldn't believe it," coach Melissa Smith said. "It was a very emotional couple of days.

"You just don't expect anything like that to happen to someone you know and work closely with."

Despite her initial fears, Carli will be in Tokyo, the athlete to be named in the Australian team on Saturday.

She will be joined at the Games by fellow Illawarra track stars Jye Edwards and Jessica Hull, the pair to contest the men's and women's 1500m events, respectively.

When the incident happened, Carli was in two minds.

On one hand, the Games were off, but on the other, Tokyo marked a goal. It was something to work towards in her recovery.

And so the rehabilitation began.

"At the time, I was pretty devastated," Carli said. "Originally the Olympics were completely off the table. But because of how rare the injury was, there wasn't any real confirmation about how long it was going to take. So I just said to myself 'I think I can still do this'.

"I held on to that hope because no one really knew, so I just told myself I was going to give it a shot. I stuck to the fact I was still going to Tokyo, that's how I thought."

A former elite athlete, Smith's relationship with Carli dates back 12 years.

As her career was winding down, she started coaching the talented teenager.

Success came quickly for Carli, the Wollongong talent winning a silver medal at 2011 World Youth Championships before injuries and university commitments led to a break from the sport.

Eventually she returned and it wasn't long before she was turning heads. Carli made a statement by defeating Lauren Boden at the 2019 Canberra Track Classic before an impressive performance at the World Championships.

Smith has been by her side throughout the journey, the pair forming a close bond.

A physio by day, managing injuries is usually her area of expertise. This time, however, was different.

"Early on it was scary," Smith said. "It was good the surgeon and Athletics Australia doctor were conservative with Sarah, that made me feel better.

"The other positive was every time I programmed something for Sarah, they approved it. There was never a point where they said 'no, it was too much'."

Carli's rehab was a painstaking process.

The hurdler was banned from any exercise for four weeks before she was allowed to start walking.

A gradual progression towards jogging followed as the volume slowly increased and she was later allowed to start sprinting.

It was a cautious approach, Carli and Smith guided by Athletics Australia officials and Wollongong surgeon Dr Tam Nguyen.

In many ways it was a case of trial and error, Carli one of few elite athletes to attempt to return to high-performance sport following a carotid artery rupture.

"These kind of injuries generally don't happen to people my age," Carli said. "Because I'm so young, so fit and healthy, I exceeded expectations quite quickly.

"Mel has been a person of strength throughout the whole situation. I definitely put her outside her comfort zone, even the doctors involved didn't know exactly what to do in my return.

"We worked closely with the Athletics Australia head doctor and my surgeon and we came up with a plan and we stuck to it."

As the months wore on, Carli's status remained uncertain.

Would she be ready for Tokyo?

In mid-June, the picture started to take shape. Carli received the green light to commence hurdling and with just two sessions under her belt she was in Townsville for her comeback race.

It was a scratchy performance, as the runner anticipated, but it was also a significant milestone.

"I was really excited to race," Carli said. "We did the best we could with the preparation that I had. It was pretty tough, I knew it would be tough but I was just happy to be allowed back on the track.

"I don't think the time reflected the kind of shape I'm in. There's definitely more there but just being back was the most important thing."

The 26-year-old knows she has to recalibrate her goals for Tokyo.

It's a frustrating situation, given how well she was running before the accident, but Carli is just thrilled to be able to compete at the Olympics.

That doesn't mean she'll be there to make up the numbers, however, the athlete determined to see how far she can progress.

"If you asked me in January, I would've said I want to make a final. Now, I'd love to get two runs and make it to the semi-final, but we will have to wait and see.

"I'm racing in Cairns in mid-July, that will be an indicator of what I can do after another month of prep."

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Smith was pleased with Carli's effort in Townsville and was quick to identify areas to work on.

The base fitness was there, the focus now turning to hitting top speed.

Should they get that right, Smith is optimistic Carli can get close to the form that saw her qualify for the Olympics.

"We've done the hard work in getting her fit again," Smith said. "Generally speed can come over a six-week period, so I'm not too concerned about that.

"Sarah's quite lucky in that she's technically good over the hurdles, so it won't take her much to get back into a rhythm. If she goes sub-56 (seconds) in Tokyo, I'll be very happy. She's only done that twice now, once in Doha then when she ran the qualifier in December."

Like so many elite athletes, Carli possesses a drive to do whatever it takes to achieve her goals. Before the accident, that was to make an Olympic final.

After the accident, it was just to get to Tokyo.

Smith has watched Carli in action for years and even she was surprised by the way her athlete responded to the life-threatening incident.

"Sarah's commitment has been ridiculous, she's just been so hungry,'' Smith said. ''Even after that first race, everyone was happy to see her back racing but she wasn't happy. She wants to run faster and get back to her best.

"It doesn't seem fair for her, she was in the best shape of her life and it got taken away from her. She's been so brave, I don't know how she was able to deal with it and process everything early on."

Regardless of the final result in Tokyo, Carli knows it's been an achievement just to even be back running, let alone compete at an Olympics.

Having experienced first-hand how quickly a career can change, the athlete is determined to ensure the Games are the start of a successful few years.

"I know I won't be going to the Olympics in my full capacity because of what happened. I'll be in the best shape under the circumstances but it's not a reflection of me as an athlete,'' she said.

"This accident has made me realise athletics is the main priority and main goal. I'll be looking to Paris with even more focus than I would've if it didn't happen. It could be a blessing for me, to have that realisation."