Alex de Minaur has delivered a huge boost to his hopes of reaching the end-of-season ATP Finals, conjuring up some of his best tennis since suffering his season-changing injury at Wimbledon as he powered into the last four at the Vienna Open.

The Australian number one had to come from a set down against one of the hottest young prospects in the world game, teenage Czech Jakub Mensik, before prevailing 6-7 (2-7) 6-3 6-4 just before midnight on Friday (Saturday AEDT) and booking a place in the semifinals.

If he can win the hardcourt title in the Austrian capital over the weekend, it would push de Minaur among the top eight players currently in line to qualify for the showpiece men's Finals in Turin next month.

Sydney's second-seed de Minaur will face unseeded Russian Karen Khachanov in Saturday's (Sunday AEDT) semifinal, while rising British star Jack Draper will meet Italy's Wimbledon semifinalist Lorenzo Musetti in the other last-four duel.

Getting into the mix for an ATP Finals place after the hip injury that has completely disrupted his program since he suffered it at Wimbledon in July would be an extraordinary feat of resilience and resolve from the 25-year-old 'Demon', who unveiled those qualities once more while subduing the brilliant Mensik.

After being blown away by the irrepressible 18-year-old in their first-set tie-break, de Minaur not only survived the barrage of 15 aces and 47 winners that scorched from the young Czech's racquet but he also became the first man all week to break Mensik's huge serve, achieving the feat once in each of the next two sets.

In some dazzling final exchanges in the deciding set, the Australian particularly amazed in one rally with a sensational reaction lobbed volley when he was seemingly flying the wrong way in mid-air.

De Minaur proved much more secure than the teenager, who made 47 unforced errors to the Australian's 19, as he set up a battle with Khachanov, who had earlier defeated Matteo Berrettini 6-1 6-4.

AAP