The text to Ash Barty from mentor Evonne Goolagong Cawley in her hour of need

When Ashleigh Barty decided to quit tennis after her biggest career high, those close to the then-15-year-old were not surprised.

The demands of being a professional tennis player had got to the teenager and she couldn't cope.

Barty had just won the 2011 Wimbledon Juniors title, having started playing on international tours the year before.

She was exhausted, lonely, confused, homesick and depressed. Barty would frequently call her parents, in tears, from her hotel room.

"It was terrible," she told the Sydney Morning Herald in 2017.

"It was all just too much. I was younger than the other girls on tour, so I knew them but not well. I just felt lonely and strange."

When she came home, Barty decided to push on with her career and moved from Ipswich, in Queensland, to Melbourne.

But a year later she realised something had to change. Barty, who was seen as a tennis child prodigy, walked away from the sport.

She had been playing since she was 5 years old. At 16, she'd had enough.

Her decision was praised by tennis legend Evonne Goolagong Cawley.

The former world number one had become friends with Barty over the years, thanks to their shared love of tennis and Indigenous heritage.

Goolagong Cawley sent Barty a text message, encouraging her to rest: "Hey darl. Good decision. Go and wet a line."

Barty took her mentor's advice and travelled to northern New South Wales, spending time fishing, at the beach and at the pub. She was close to her family.

"I was so relieved," Barty said.

"It was a weird time, but as soon as I got it off my chest I was so much better."

Barty's dad, Robert, told the Herald he thought he'd passed on his depression to his daughter. He encouraged her to get professional help and that she did. Barty took medication for two years and saw a therapist.

In her break from tennis, sport was never far away. She started coaching and turned to cricket, eventually playing for Brisbane Heat in the Women's Big Bash League.

Speaking of her career break following her defeat of Sharapova on Sunday, Barty said, "I needed to take that time away. I feel like I came back a better person on and off the court, a better tennis player.

"For me, having that 18 months off was vital."

Barty eventually came back to tennis after her doubles teammate, Casey Dellacqua, dragged her onto an empty court after the 2016 Sydney International.

She officially returned to the sport in June, 2016, and worked hard to get her ranking back.

Following Barty's 2017 Newcombe Medal win, Goolagong Cawley said: "When I watch Ash play now, it makes me want to play again. She has all the skills of becoming a real champion. She has the hands and she has the power. A volley and a big serve. The way she’s going now, [a major title] is possible one day. I watch her and I think, 'Wow, that must feel good'."

Barty is now ranked 15 in the world and is seeking her first ever Grand Slam win at the Australian Open.

When she steps out at Melbourne Park for the quarter finals of the Australian Open today, Barty will be the first Australian women to do so in 10 years, since Jelena Dokic's run in 2009.