MELBOURNE: Russian qualifier Aslan Karatsev became the first player to reach a Grand Slam quarter-final on debut in 25 years Sunday, stunning 20th seed Felix Auger-Aliassime at the Australian Open.

The power-hitting 27-year-old, a virtual unknown before the tournament started, battled back from two sets down to upset the Canadian 3-6, 1-6, 6-3, 6-3, 6-4 on Margaret Court Arena.

It continued his giant-killing run after blitzing eighth seed Diego Schwartzmann in round three, setting up a quarter-final clash with either world number three Dominic Thiem or Grigor Dimitrov.

“It was really tough in the beginning to play against him. He played really fast and it took me two sets to find a way how to play,” he said.

He is the first qualifier to achieve the feat since Australia’s Bernard Tomic at Wimbledon in 2011 and only the third ever at the Australian Open after Bob Giltinan in 1977 and Goran Ivanisevic in 1989.