Aussie teen Alexei Popyrin, wildcard Alex Bolt into Australian Open third round

Another Australian teen sensation Alexei Popyrin and Victorian wildcard Alex Bolt are into the third round of the Australian Open after upsetting seventh seed Dominic Thiem (who retired) and 29th seed Gilles Simon respectively.

The 19-year-old Popyrin was well on top before the Austrian and 2018 French Open finalist called it quits while trailing 7-5, 6-4, 2-0.

Thiem, who had a five-set first round win, called for the trainer midway through the second set citing general fatigue.

Wildcard Popyrin, who had only played one grand slam match before this tournament looked fearless.

Using his big forehand weapon, Popyrin hit almost double the winners of Thiem, who looked sluggish from the outset.

Despite standing 195cm Popyrin showed impressive speed around the court as he pressed the tiring Thiem.

Popyrin said he felt in control after wrapping up the second set.

"It is never easy winning like this -- Dominic played a tough first round," Popyrin said.

"I always thought that I was in the match to be honest but when I won the second set is when that thought really kicked in and that I could actually win the match."

Later, wild-haired wildcard Alex Bolt treated fans on Court 3 to a pulsating second-round win over veteran Frenchman Gilles Simon.

Bolt saved four match points in a thrilling 2-6, 6-4, 4-6, 7-6 (10-8), 6-4 fightback over the former world No. 6 to leave fans on Court 3 in a frenzy.

"This is the best thing I have ever experienced in my life," the world No. 155 said.

"It is unbelievable to have everyone behind me tonight. They really got me over the line."

With fellow wildcard Alexei Popyrin getting past 2018 French Open finalist Dominic Thiem, who retired trailing by two sets earlier on Thursday night, Australia has five men and women in the last 32 at Melbourne Park for the first time since 2004.

"I think we are in a pretty good spot. Hopefully some of us can win another round and go deeper into the tournament," Bolt said.

Bolt smoked 43 forehand winners against the 29 seed Simon, backing up his maiden grand slam win on Tuesday over American Jack Sock.

The 26-year-old, who took a break from tennis three years ago to work as a labourer with his brother, had never before beaten a player ranked inside the top 70.

"My parents have come over from Murray Bridge. To be able to perform like this in front of them is real special," he said.

Big guns Ashleigh Barty and Alex de Minaur will keep the flag flying on Friday when they play Greek Maria Sakkari and Rafael Nadal respectively, while wildcard Kimberly Birrell faces second seed Angelique Kerber.

The last group of five Australians to make the third round was Mark Philippoussis, Lleyton Hewitt, Todd Reid, Nicole Pratt and Alicia Molik.

Bolt will meet either German fourth seed Alexander Zverev or Frenchman Jeremy Chardy for a place in the fourth round.