Former Australian Open runner-up Danielle Collins will have to bring her A-game to once again stop world No.1 Iga Swiatek in her tracks at Melbourne Park.
Polish superstar Swiatek was denied an Open final showdown with Australian Ash Barty in 2022 when stunned by Collins in the semis.
Two years on, the unseeded American shapes as a potential stumbling block in Swiatek's quest to add a maiden Melbourne title to her haul of four grand slams.
Collins, who battled past new mum and 2016 Open champion Angelique Kerber first up, is under no illusion things will get easier on Thursday when she meets Swiatek on Rod Laver Arena.
"Iga's game speaks for itself. She kind of has all the tools," she said.
"We're very familiar with her game and I've played her a couple of times and had some great matches with her and some not-so-great matches with her.
"So hopefully I can have one of my best days on court, because against the best players you have to bring your best."
After extended her winning run to 17 matches with an opening-round victory against 2020 Open champion Sofia Kenin, Swiatek acknowledged Collins shapes as another tough match-up.
But she pointed to her 6-1 6-0 win over the American world No.62 at the Cincinnati Masters in August.
"We played really tight matches. On the other hand our last match ... from the score, I had it under control," the Pole said.
Ajla Tomljanovic is among three Australians in action on day five, squaring off against rival and 11th seed Jelena Ostapenko.
The 30-year-old local hope set up a rematch of her infamous clash with the Latvian at Wimbledon in 2021 with a first-round comeback win over Croatian Petra Martic.
Australia's three-time grand slam quarter-finalist complained when Ostapenko called for a medical time-out at the All England Club three years ago, sparking a war of words.
But ahead of their clash Tomljanovic insisted there was no bad blood between the pair.
On the men's side of the draw, Thanasi Kokkinakis and Max Purcell will have their work cut out for them against seeded stars Grigor Dimitrov and Casper Ruud respectively.
Spanish gun and world No.2 Carlos Alcaraz will also be seeking to equal his best performance at Melbourne Park with victory over Italian Lorenzo Sonego.
AUSSIES IN ACTION ON DAY FIVE OF THE AUSTRALIAN OPEN (PREFIX DENOTES SEEDING):
Men's singles, second round
Max Purcell v 10-Casper Ruud (NOR)
Thanasi Kokkinakis v 13-Grigor Dimitrov (BUL)
Women's singles, second round
Ajla Tomljanovic v 11-Jeļena Ostapenko (LAT)
