Stefanos Tsitsipas reached the Australian Open semifinals for the fourth time as the Greek saw off rising Czech Jiri Lehecka 6-3, 7-6(2), 6-4 on Tuesday.
The third seed dominated the opening set after breaking a nervy Lehecka early on but was pushed hard after that against the 21-year-old who has enjoyed a breakout tournament.
Lehecka, who had never won a Grand Slam match before arriving in Melbourne, used his powerful baseline game to stay with Tsitsipas in the second set but the Greek raised his game to ease through the tiebreak.
Tsitsipas was forced to save three successive break points at 3-3 in the third set as Lehecka threatened to extend the Rod Laver Arena clash.
The 24-year-old then pounced with Lehecka serving at 4-5, reaching match point with a searing backhand pass and wrapping up victory as his opponent netted a backhand.
Tsitsipas will face Russian Karen Khachanov in the semifinal.
Khachanov reached the semifinals of the Australian Open for the first time after ailing American Sebastian Korda retired while trailing 7-6(5), 6-3, 3-0.
The 18th seed raced out to a 4-1 lead before Korda calmed his nerves to force a tie-break but the Russian hit back to win the first set with a backhand scorcher.
Korda, whose father Petr had triumphed at Melbourne Park in 1998, struggled on his forehand and had his right wrist strapped midway through a tight second set before Khachanov broke to go up 4-3 and the 26-year-old held firm to double his advantage.
With his injury affecting his rhythm and the match slipping away, 29th seed Korda dropped serve early in the third before throwing in the towel.