Williams trails only Margaret Court in that category, and she came painfully close to tying her record past year in at Wimbledon and the US Open, losing in the final of both events to Angelique Kerber and Naomi Osaka, respectively. He expects her to be in the title mix going forward.
The 21-year-old Zverev appears the most likely of the younger generation of players hoping to end the world's top three's domination of Grand Slams, having beaten Federer and Djokovic at the ATP Tour Finals in London last November.
Two of the older generation who have shown they do have that ability - Britain's Andy Murray and Switzerland's Stan Wawrinka - could be risky floaters in the draw as they make their way back from injury-plagued seasons.
Caroline Wozniacki is also looking to defend her title after winning her first career major at this event past year.
"In general, it's about her offensive game", Rittner told Deutsche Welle of the three-time Grand Slam champion who lost an agonising, breathless semi-final 9-7 in the final set to Halep in Melbourne a year ago.More news: US Says China Willing to Buy More American as Trade Talks End
Halep cloud: World number one Simona Halep of Romania comes into the tournament under a fitness cloud after a nagging back injury curtailed her 2018 season.
"The first time I came back here and hit on the courts, I thought, 'OK, I'm home, '" the third-seeded Wozniacki said of her return to Melbourne Park.
"I don't think tarnished is the word", she told reporters via a conference call.
A second Australian Open title will be a ideal birthday gift for world number two Angelique Kerber, who turns 31 in the first week of the tournament.More news: Man accused of stealing roommate's winning $10 million lotto ticket arrested
The Romanian bounced back from losing to Wozniacki in an epic Melbourne final 12 months ago to claim her own maiden Slam at Roland Garros and climb back to number one despite a nagging back injury that forced the 27-year-old to miss the WTA Finals in Singapore.
She has looked sharp at the Hopman Cup and maintained her 100 percent singles record even though Germany lost to Federer's Switzerland in the final.
The Wimbledon champion and world number two will turn 31 on January 18 and is tipped to unveil a more aggressive approach under new coach Rainer Schuttler, who reached the Australian Open final in 2003 where he lost to Andre Agassi.
Also in the mix is the popular Osaka, who stunned Williams in NY.
Osaka suffered a straight set loss to Lesia Tsurenko in the semi-final of the Brisbane International and withdrew from the Sydney International in frustration.More news: Packers hire LaFleur as head coach
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