Alex de Minaur has been outplayed in the Vienna Open semifinals by an inspired Karen Khachanov, with the comprehensive defeat dealing a grievous blow to the Australian's dogged pursuit of a place in the ATP Finals.

Looking at times flat and still not at his sharpest since his hip injury woes, de Minaur still summoned some fire and pride near the end of a one-sided affair as he succumbed 6-2 6-4 to the Russian, whose superb form could earn him a second title in the space of seven days on Sunday.

Khachanov has carried on where he left off in the Almaty Open in Kazakhstan, when he also beat Australian Aleksandar Vukic, in the semifinals on the way to the title.

His win over world number 10 de Minaur was his eighth in a row over the past fortnight and sets up a final against British number one Jack Draper, who had earlier on Saturday beaten Italian Lorenzo Musetti 6-2 6-4 in the other semi.

For de Minaur, though, a familiar battling effort was not enough to get him to a fourth final of the year, which he would have needed to win to join the top eight players of the season who are currently heading for the year-ending men's championship in Turin next month.

De Minaur's hopes keep flickering as he moves on to the Paris Masters, still in ninth spot — one place behind Andrey Rublev. But there were times during his heavy beating by Khachanov when he still looked physically a shadow of the player who'd been enjoying such a brilliant season until his hip injury flared up at Wimbledon.

At the moment, after just his third tournament since that blow in July, he seems to be relying on seemingly endless reserves of courage and resilience but when faced with a currently super-charged world No.24 Khachanov, that simply wasn't enough.

During a weird opening to their contest, second seed de Minaur's first service game was interrupted at some length by a noisy, seemingly inebriated spectator seated next to Khachanov's team.

The man had to be persuaded by stewards to leave the arena or be escorted out by security, and was applauded and whistled at by the crowd as he made his long overdue exit.

In the middle of a tight game, that delay had been the last thing de Minaur needed and, on resumption, he went on to get broken, a misstep that Khachanov took full advantage of as he started unleashing the first salvos among his blistering 27 winners.

De Minaur was broken again in the first set, apparently as uncomfortable when trying to push off from his right hip as he was when attempting to deal with the searing pace of Khachanov's groundstrokes.

Khachanov was playing so well that, at 4-2 down in the decider, de Minaur could only end up stepping back and applauding one glorious cross-court winner from the Russian on the way to being broken for a fourth time.

Yet, throwing caution to the wind at 5-2 behind, de Minaur hit back belatedly and valiantly, earning his first break from nowhere and forcing the Russian to serve for the match a second time.

The Aussie saved a match point at 5-4 down, but, ultimately, couldn't stop Khachanov from sealing the win in just under an hour and a half.

AAP