Another Australian teen sensation Alexei Popyrin is into the third round of the Australian Open after Dominic Thiem retired midway through the third set of their Melbourne Arena clash.

The 19-year-old surprise packet was well on top before the Austrian seventh seed 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.”