Rampant Tsitsipas charges into Open semis

Stefanos Tsitsipas has charged into his fourth Australian Open semi-final in five years as he chases an elusive breakthrough grand slam title.

Tsitsipas worked his way through the gears against Jiri Lehecka on Rod Laver Arena on Tuesday night to bring the young Czech's fairytale run to a grinding halt with an impressive and mature 6-3 7-6 (7-2) 6-4 victory.

The No.3 seed is the highest-ranked player left at Melbourne Park and will face Russian Karen Khachanov for a spot in the final.

"It felt different this time from any other match but the most important thing is I found a solution," Tsitsipas said.

"It was a very difficult three-setter, one of the most difficult ones I had so far in the competition.

"I had to deal with the ground strokes, they were coming over the racquet from the other side of the court much heavier, much deeper.

"So that was a task in which I really had to put my heart out there and give it my best."

Tsitsipas reeled off the first set in just 36 minutes and looked in ominous form.

To Lehecka's credit, the 21-year-old, who previously accounted for Felix Auger-Aliassime and Cameron Norrie, took it up to the Greek star in the next set.

But Tsitsipas kicked up a gear, reeling off the first four points of the tiebreak and claiming the set comfortably.

"The way I saw it, that was my opportunity to really take a massive lead there and I'm really happy with the way I closed the second set," he said.

Lehecka earned three break points at 3-3 in the third set but Tsitsipas showed impressive composure to haul back the game and take the lead.

But he lamented a moment at 4-3 when out of frustration, he hit the ball into the back wall, a couple of metres away from an advancing ball kid, risking a default if he'd hit them.

"I'm a professional tennis player. I was not aiming for the ball kid obviously. I saw the wall, just went back towards the wall," he said.

"The ball kid, in my eyes, was pretty far away from me. Would have really had to miss to hit that ball kid.

"Of course, it's not nice even to hit it back towards the wall. I personally don't think I hit it too hard. But doesn't matter. Doesn't matter.

"What I did, definitely I'm not happy about that. I shouldn't have done it."

The 24-year-old earned his first match point when receiving at 5-4 in the third set and converted it.

Tsitsipas will next take on 18th seed Khachanov, who was leading Sebastian Korda 7-6 (7-5) 6-3 3-0 when the American retired with a wrist injury.