One player relived the glory days on centre court while the other is just starting to create her own history.
Molik needed a wild-card to enter the main draw but destroyed the morale of world No 37 Roberta Vinci , of Italy, in the 1-6 6-3 8-6 first round thriller .
Conversely, Stosur barely raised a sweat as she showed no mercy to American wild-card Lauren Davis, 17, and won 6-1 6-1.
Alicia Molik and Samantha Stosur remain the main Australians in the draw since the elimination of Lleyton Hewitt and Jelena Dokic. Both will highlight day 4 at Rod Laver Arena.
The top half of the draw will be played on the Men's side, while the bottom half of the draw will seal the second round stories on the Women's side.
World number one Rafael Nadal will also be in action against American Ryan Sweeting, as will 2009 US Open champion Juan Martin Del Potro, who will take on Marcos Baghdatis in a blockbuster match.
Alicia Molik will have to play even better than what she did in the first round when she takes on Russia's Nadia Petrova.The pair have met twice before - both times in 2004 on hard courts - and have one win each.But back then Molik was a top-30 player on her way to a career-high ranking of No.8 the following year, when she also reached the Australian Open quarter-finals.
That 2005 appearance at Melbourne Park, when she beat Venus Williams in the fourth round, remains her best Grand Slam showing.
Since then, she has retired, returned, and worked her way back up the rankings from the low 300s. She is now 134th.But if she can play against former world No.3 Petrova with the same liberation she displayed earlier this week, she will have played with the freedom that comes with learning from the many highs and lows of a long career.
The essential challenge confronting Molik is that Petrova's shots are superior, and she's also not afraid of the net. It might take an out-of-body experience for the local favorite to prevail, but she'll leave everything on the court in trying.
Molik, who turns 30 next week, is approaching the twilight of her career .
Sam Stosur (AUS)
The Queenslander will be favorite going to her next match against the Russian, while leading 2-1 in their head-to-head meetings. Both players met in Charleston last year on clay and Stosur prevailed 6-1 3-6 6-1. Molik claimed her first mixed doules title with Scot Draper at the Australian Open back in 2005, but then realised she might have a role to play in the singles competition.
The 26-year-old Gold Coast resident is a former world No. 1 on the WTA Tour in doubles with Lisa Raymond from the United States. In singles, Stosur has wins against former No. 1s Ana Ivanovic, Jelena Jankovic, Serena Williams, Dinara Safina, Lindsay Davenport, Amélie Mauresmo, Justine Henin and Caroline Wozniacki. Her career high in singles was World No. 5, achieved on July 5, 2010. Stosur remains currently ranked World No. 5 in singles. The Aussie was runner up in singles at the 2010 French Open, reaching her first major final for the first time ever.
It's one of the very few attacker in the game being so comfortable on clay.
The slow surface of Melbourne Park could help her win her first major if she can deal with her nerves. When Stosur is on fire she can play like Federer.
On the other side of the net Dushevina's best result at a Grand Slam came at the 2005 Australian Open, when she reach the last 16 round.
Watch out for Juan Martin Del Potro!
The Argentine, on the mend from a wrist injury, beat Israeli Dudi Sela for his first win at a major in 12 months.
Del Potro highlights Day 4 Men's singles, facing Marcos Baghdatis in what could be yet another thriller in Melbourne.
Many tennis fans might remember Del Potro when became the newest member of the Grand Slam title club when winning the 2009 US Open. He is the only player to defeat both Rafael Nadal and Roger Federer at a Grand Slam tournament.
Del Potro didn't get the chance in 2010. After losing to Marin Cilic, who possesses a similar game, in the fourth round of the Australian Open, the soft-spoken 22-year-old took an extended break due to his surgery.
Don't expect The tall man from Tandil, Argentina to re-enter the top 10 in the coming weeks. But it's likely a matter of when, not if. His most pressing concern is Baghdatis, no stranger to injuries himself. Baghdatis loves Melbourne, having surprisingly reached the final in 2006, and is fitter than ever.
This is Marcos’ most successful Grand Slam event. He has an 18-6 win-loss record here, compared to a 2-5 win-loss record at the US Open – his least successful Grand Slam event.
Del Potro leads Baghdatis 1-0 in their head-to-head meetings, with the Argentine defeating the man from Cyprus 6-2 5-7 6-0 back in 2007 at Key Biscayne.
Top seed Rafael Nadal didn’t lose a game in his opening round match with Brazil’s Marcos Daniel. Today’s opponent, 23-year-old American qualifier Ryan Sweeting, is looking to stop the Spaniard from becoming just the 3rd man in history to win 4 consecutive Grand Slam titles.
Mission Impossible? After all the qualifier could take some advice from France's Gilles Simon, who gave Roger Federer a hard time in the office. The Swiss needed five sets to overcome the intelligence of the former world number 6.
However the American doesn't have the experience Simon has.
The ranked number 116 in the world is looking to reach the 3rd round at a major for the first time in his career.
It will be Sweeting’s 8th Grand Slam. The only other time he has advanced past the 1st round at a major was on his Grand Slam debut at the 2006 US Open.
It is also worth mentioning Sweeting has never defeated a Top 10 player in 2 previous meetings and both players have never met before.
John Isner certainly knows he can't afford to loose focus on his first major of the season, because the Czech veteran is a wily, tricky character who can upset anyone -- as he's proved.
Stepanek's low ranking of 66th is courtesy of a knee injury and mono, both surfacing last year.
The man from Czech Republic is looking to equal his best Australian Open performance by reaching the 3rd round. He reached the same stage here in 2003, 2005, 2007 and 2009.
Radek’s best Grand Slam result to date is reaching the quarterfinals at 2006 Wimbledon.
At 32 years 2 months, the Karvina native is one of 7 men aged over 30 to reach the 2nd round here. The tall American will also be well aware of his 6-3 6-2 loss to Stepanek at the Nottingham Open back in 2008.