Sloane Stephens and Jelena Ostapenko did it last year.
Just don't describe the first Grand Slam of the year as "more open" than usual.
"Whenever I get asked that question, it always comes across in really kind of an almost negative way instead of acknowledging how many great players we have," Johanna Konta, who reached the semifinals of Wimbledon last year, said in her pre-tournament news conference Saturday.
"The depth in women's tennis, I really do believe in the last few years, has gotten so strong," she added. "There's no straight sailing to the quarters or semis. It doesn't exist."
Stephens agrees the Australian Open field is still extremely tough, even without Williams, the 23-time major winner. Williams withdrew from the tournament to recover from health issues after a complicated childbirth in September.
"There's a lot of great players," Stephens said. "It's up for grabs."
A new face will be holding the trophy at Melbourne Park in two weeks. The No. 1-ranking changed seven times in 2017, with five different women assuming top spot - three for the first time.
Top-ranked Simona Halep is looking to finally break through and win her first major after twice finishing runner-up. She won the season-opening Shenzhen Open in China, but has mixed results at Melbourne Park, losing in the first round the last two years.
"I don't feel pressure. I feel OK. I feel fit. I feel ready to start," Halep said. "I have one more goal: to win a Grand Slam."
Stephens made a stellar run to the U.S. Open title after missing several months with an injured left foot. She's struggled to adjust to the sudden stardom that's come with being a Grand Slam champion - losing seven straight matches since September - but believes she can find her game again in Melbourne.
"I think it's always a tough transition when you go from not playing tennis for 11 months to winning a Grand Slam," she said. "I like to just stay in my own little bubble and do my own thing. ... It's kind of been what I'm trying to do."
There are plenty of other contenders. Ostapenko, now 20, rocketed up the rankings after her stunning win at the French Open. Venus Williams is a threat at 37 years old after finishing runner-up to her sister last year. Angelique Kerber, the 2016 Australian Open winner, won the Sydney International title on Saturday.
Garbine Muguruza is the reigning Wimbledon champion, though her health has been in question at the start of the new year. Caroline Wozniacki had a career-reviving 2017 season and could return to the No. 1 ranking for the first time in six years with a strong showing in Melbourne.
Maria Sharpova, the 2008 winner, returns after missing last year's Australian Open because of a drug suspension.
And then there's Elina Svitolina, who earned her 10th tour title last week at the Brisbane International. She has a shot at No. 1 during the Australian Open.
"I had a great week in Brisbane. Of course, I'm confident," she said.
But she added that isn't enough in the constantly shifting, ultra-competitive women's game.
"Everyone wants to win a Grand Slam," Svitolina said. "So, I try to find my way, what can help me to be there, to be ready for the fight."
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