Open semi-finalist Khachanov is a believer

Russian Karen Khachanov's self-belief is sky high after taking advantage of an injury to Sebastian Korda to book his maiden Australian Open semi-final spot.

Khachanov was the first man through to the final four when Korda retired at 0-3 in the third set, ending the American's dreams of adding to the family folklore with his father Petr Korda winning the Open in Melbourne in 1998.

"Back-to-back semi-finals in a grand slam feels great," said 18th-seeded Khachanov after the 7-6 (7-5) 6-3 3-0 victory.

"It's obviously not the way you want to finish a match and I think until a certain point it was very competitive and a good battle.

"Sebastian beat one of my friends, Daniil (Medvedev) in three sets, and five sets against (Hubert) Hurkacz, so you know he's playing great tennis.

"I'm feeling good and really happy about my level and the way I compete and looking forward to semi-finals here in Australia for the first time."

He will face Greek third-seed Stefanos Tsitsipas, who beat unheralded Czech Jiri Lehecka 6-3 7-6 (7-2) 6-4, for a spot in the final.

Khachanov also reached the final four at last year's US Open after beating Australian Nick Kyrgios in five sets in the quarter-finals and said it had changed his mindset.

He was beaten in the semi-finals there by Norwegian Casper Ruud in four sets.

"Sometimes when you have those great results it shows you what you're capable of so you believe more and more," the 26-year-old said.

"This belief and self confidence appears much stronger after the US Open.

"I think with my team, we are on the right direction and the right move."

The 18th seed started strongly and raced to a 5-2 lead before Korda found his groove and pushed the opening set to a tie-break, showing no signs of injury.

But he took a medical time-out while leading 3-2 in the second and had his right wrist strapped.

It didn't appear to help and with his error count mounting Korda dropped the next seven games.

The 22-year-old, who was playing in his first grand slam quarter-final, briefly left the court between the second and third sets and then tried in vain to continue before calling it quits.

He said he was unsure how serious the injury was, first feeling it in the Adelaide International.

"I had it a little bit in Adelaide a couple weeks ago, but then it went away," world No.31 Korda said.

"Then just one kind of mis-hit return, and it started to bother me a lot after that.

"Some forehands I couldn't even hold the racquet and volleying was almost impossible for me so it was a little tough.

"I will see a doctor right after this and figure out more."

There's a possibility of an all-Russian final with world No.6 Andrey Rublev also still in Melbourne. He takes on nine-time champion Novak Djokovic in a quarter-final.