Below-par Novak Djokovic faces fresh Australian Open test
The Serbian top seed spent more than three hours on court on Wednesday against Alexei Popyrin after a gruelling first-round match.
His bid for an 11th Melbourne title and record-breaking 25th Grand Slam crown will resume on Rod Laver Arena in the evening against in-form Argentine Tomas Martin Etcheverry, who ended Andy Murray's tournament before ousting Gael Monfils.
"His results are really impressive, he's obviously playing maybe the tennis of his life on the hard court," Djokovic said of the 30th seed.
"I have to be very, very prepared and ready for that."
The world number one and top seed has been under the weather this week, regularly blowing his nose, and admitted he has not been at his best.
"It's frustrating at times with kind of the level of tennis that I'm playing on the court and some uncharacteristic mistakes that I make," he said.
"Hopefully things will go in a positive direction in terms of how I feel and play."
Andreeva, just 16, stunned sixth seed Ons Jabeur for the loss of just two games to make the third round, where she faces France's unseeded Diane Parry on an outside court, herself only 21.
Ranked 47, Andreeva burst onto the scene when she reached the fourth round at Wimbledon last year as a qualifier and will be attempting to match that accomplishment on Friday.
Another young Russian, Maria Timofeeva, is back on court after upsetting former champion Caroline Wozniacki and will meet Brazilian 10th seed Beatriz Haddad Maia.
Defending champion Aryna Sabalenka was pitted against teenage qualifiers in her opening two matches and wasted little energy swatting them aside.
But she will face a stiffer test on centre court against Ukrainian 28th seed Lesia Tsurenko, a former US Open quarter-finalist.
Jannik Sinner, Andrey Rublev and Stefanos Tsitsipas, seeded four, five and seven, are also in action.
In the women's draw, US Open champion Coco Gauff resumes her charge towards a maiden Australian title against fellow American Alycia Parks while Amanda Anisimova faces Paula Badosa.
