Simona Halep is the No.1 seed at a Grand Slam for the first time in her career - but is looking to snap a three-match, six-set losing streak in Melbourne dating back to the 2015 quarterfinals. Then, the Romanian lost to Ekaterina Makarova 6-4, 6-0, and in her two subsequent visits lost in the first round to Zhang Shuai 6-4, 6-3 (in 2016) and Shelby Rogers 6-3, 6-1 (in 2017). The last Australian Open women's No.1 seed to fail to reach the second week was Virginia Ruzici - now Halep's agent - in 1979, who lost to Australia's Mary Sawyer 0-6, 6-2, 6-4 in the first round. Halep also faces an Australian today, 17-year-old Destanee Aiava.
No.28 seed Mirjana Lucic-Baroni is already the only 2017 semifinalist remaining in the draw. Serena Williams, continuing to recover from giving birth, withdrew from the tournament last week; while Venus Williams and CoCo Vandeweghe lost their opening matches yesterday.
No.21 seed Angelique Kerber has opened 2018 with a nine-match winning streak, having won four matches in the Hopman Cup and five last week to win the Sydney International. The German has dropped just two sets in this run - to Lucie Safarova and Venus Williams in the first two rounds of Sydney.
No.27 seed Petra Kvitova will resume a rivalry locked at 4-4 against Andrea Petkovic today. The Czech won their only previous match on Australian hard courts, taking the 2011 Brisbane final 6-1, 6-3, and has not lost a set to Petkovic in their two meetings since Cincinnati 2011.
No.18 seed Ashleigh Barty is competing at her home Slam as a seed for the first time, having entered via wildcard on each of her previous four Australian Opens. Remarkably, despite having started 2017 ranked No.271, she would only lose to three opponents outside the Top 50 all year - Risa Ozaki in Hobart, Mona Barthel at the Australian Open and Sloane Stephens at the US Open. Today, she faces World No.66 Aryna Sabalenka.
No.11 seed Kristina Mladenovic faces World No.104 Ana Bogdan, who is yet to crack the Top 100 despite competing in her sixth Slam main draw, all via either direct entry or qualifying, and winning a round three times. Bogdan also holds a winning record against Top 20 players, 2-1, with victories over Anastasija Sevastova in the Bucharest quarterfinals last year and Elena Vesnina five weeks later in the first round of New Haven. Mladenovic will be seeking to snap a 14-match losing streak.
American wildcard Kristie Ahn is competing in the second Slam main draw of her career - a decade after the first. As a 16-year-old qualifying wildcard, she navigated her way to the main draw of the US Open in 2008, losing 6-3, 6-4 to Dinara Safina. Since then, she's gone to Stanford University, graduated with a major in Science, Technology and Society, turned professional and currently sits at a career high of No.105.
In Anna-Lena Friedsam's last appearance at the Australian Open in 2016, the former World No.45 reached the fourth round, where she led No.4 seed Agnieszka Radwanska 5-2 in the deciding set before succumbing 6-7(6), 6-1, 7-5. A shoulder injury kept Friedsam out for most of 2017, but since her return in September the German has raised her ranking to No.388, winning the first WTA match of her comeback last week in Hobart over Alison Van Uytvanck. She will face 2016 champion Angelique Kerber today.
Carina Witthoeft, who faces No.8 seed Caroline Garcia today, is 0-8 against Top 10 opposition in her career, with only two sets won in those matches, and 0-2 against Garcia. However, the German's best career win to date came in the first round here in 2015, over No.17 Carla Suárez Navarro.
No.9 seed Johanna Konta has never lost before the quarterfinals in her two previous main draw appearances. She is 1-3 against her first round opponent, Madison Brengle - although the first two losses were via retirement, and the Briton won their most recent match 6-4, 6-0 in the first round of Indian Wells in 2016.
Joel Drucker's in-depth analysis for Tennis.com of Belinda Bencic's upset of Venus Williams is a reminder of the Swiss 20-year-old's rare talent.
Heather Watson spoke to the Telegraph's Simon Briggs about how playing ITF tournaments during her spell outside the Top 100 has motivated her.
ORDER OF PLAY
Find out when and where players are up on the second day in Melbourne.
World No.47 Tatjana Maria's first-round opponent is ranked one place beneath her - but given that it is 2008 champion Maria Sharapova, it's a formidable test. The German talks to wtatennis.com about how she feels ahead of the match.