MELBOURNE -- Here are the best matches to watch as the second day of the tournament gets underway on Tuesday morning in Melbourne:
Serena and Venus Williams get underway
It's odd to see an order of play listing the WTA No. 1 on the secondary court (7 p.m. local time/3 a.m. ET, Margaret Court Arena) while the featured night match on Rod Laver Arena is No. 67 Ajla Tomljanovic vs. No. 76 Shelby Rogers.
The decision can be explained by the new Australian flag flying next to Tomljanovic's name. Serena will surely put any thoughts of a slight aside. She needs to throw down a decisive performance against Belgian Alison Van Uytvanck.
Big sister Venus, seeded 18th, will feature in the evening match on the cavernous Hisense Arena against Maria Torro-Flor.
Victoria Azarenka and Sloane Stephens revisit their Australian Open rivalry
All you need to know about the last two years of Azarenka and Stephens' careers can be traced to their Australian Open clashes. The two played a controversial semifinal in 2013 -- the famous "Choke of the Century" match -- which Azarenka won 6-1, 6-4. The former No. 1 would go on to win her second Australian Open title, while Stephens' semifinal run, which saw her beat Serena Williams, would launch her into the spotlight. When they met again last year it was in the fourth round. The match fizzled under the hype. Azarenka won easily again, 6-3, 6-2, but the two would go on to slump in 2014.
Azarenka was sidelined most of the year with injuries, while Stephens struggled with the pressure of trying to back up her breakout season. By the end of the season their rankings plummeted, and they now meet in the first round as non-seeded players. Azarenka has looked the sharper player in the pre-tournament lead-ups.
The winner of the match will play the winner of the other highlighted first round match of the day, the matchup between Caroline Wozniacki and Taylor Townsend (second match, Margaret Court Arena). The two played just two weeks ago at the ASB Classic and Townsend came very close to taking a set off the Dane but lost 6-1, 7-6.
Novak Djokovic, Stan Wawrinka and Kei Nishikori begin their tournaments
While No. 1 Djokovic is the favorite to win his fifth Australian Open title, Wawrinka has show good form as he enters as defending champion and Nishikori is the sexy outside pick to breakthrough to be the first of the next line of players to win a major. Wawrinka plays Marsel Ilhan (second match, Rod Laver Arena) and Djokovic could have a tricky one agianst Aljaz Bedene (third match, Rod Laver Arena). The Slovenian made a surprise run to the Chennai Open final two weeks ago. Nishikori faces the potentially dangerous Nicolas Almagro (first match, Rod Laver Arena), but the Spaniard is coming back from injury and wasn't even sure he would play the tournament.
More matches to watch
Agnieszka Radwanska  vs .Kurumi Nara (fourth match, Show Court 2): With the slew of upsets on Day 1, no one is safe. No. 39 Nara is a quality player who was seeded at the U.S. Open. Radwanska won their only match 6-2, 6-2 last year on hard courts.
Andrea Petkovic  vs Madison Brengle (second match, Court 6): Brengle isn't a household name when it comes to American women's tennis but she's had a very good start to the season, making her first WTA final last week at the Hobart International as a qualifier. Petkovic, meanwhile, is 0-2 to start the year. Upset alert.
Flavia Pennetta  vs. Camila Giorgi (third match, Court 6): Two Italians facing off with one (Giorgi) willing to hit for the lines on every swing? This could be explosive. And if you get bored, just keep your eye on Giorgi's excitable father, Sergio. You can't miss him.
Sam Querrey vs. Vasek Pospisil (fourth match, Court 6): Not an easy first round draw for either man, especially for Querrey, who comes into the match 0-2 on the season.
Madison Keys vs. Lesia Tsurenko (fourth match, Court 12): Keys narrowly missed out on a No. 32 seed. Her lead-up was a mixed bag: great wins over Dominika Cibulkova and Svetlana Kuznetsova followed by a brutal loss to Varvara Lepchenko and an injury withdrawal due to her right shoulder. Tsurenko has never seen a ball she didn't want to bash. Might want to bring a helmet to this one.
Roberto Bautista Agut  vs. Dominic Thiem (second match, Court 13): Thiem's best buddy Ernests Gulbis has never been shy bout letting the world know about his lack of respect for the Spaniard, who he insists on calling "The Princess". Nice opportunity for Thiem to score the upset.
Jelena Jankovic  vs. Timea Bacsinsky (third match, Court 13): Bacsinszky started her season with a fantastic run to the Shenzhen Open final, where she beat Petra Kvitova in the semifinals. To say she's the more in-form player in this match-up is a dramatic understatement.