Stefanos Tsitsipas defeated Jiri Lehecka in straight sets to set up an Australian Open semi-final with Karen Khachanov.
Greek third seed Tsitsipas reached his fourth Melbourne semi-final in five years with a 6-3 7-6 (7-2) 6-4 win.
Russian Khachanov progressed to the final four of the Australia major for the first time when his quarter-final opponent Sebastian Korda was forced to retire with a wrist injury with the score at 7-6 (7-5) 6-3 3-0.