Australian tennis star Alex de Minaur is in a desperate race to reach the end-of-season ATP Finals, and he’s returned to form just in time.

He has just produced some of his best tennis in a long time (including one stunning shot in the final set that blew everyone away), coming from a set down to defeat talented Czech teenager Jakub Mensik, 6-7 (2-7) 6-3 6-4 at the Vienna Open.

WATCH THE VIDEO ABOVE: Alex de Minaur wows with amazing lob volley.

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De Minaur wrapped up the match just before midnight on Friday (Saturday AEDT) and has now booked himself a place in the semi-finals.

But de Minaur still needs crucial points to move up the order on the ATP rankings to make the end-of-year finals in Turin next month.

The win puts de Minaur behind Andrey Rublev (seventh with 4070 points at the time of writing), and Casper Ruud (3855) who occupies the eighth and last place in the ‘Race to Turin’ standings.

If tenth-placed de Minaur wins the Vienna title, (Grigor Dimitrov is ninth on with 3740 points, narrowly ahead of the Aussie by just 15 points) he could surpass Ruud with only one more qualifying event left at the Paris Masters over the next fortnight.

He could also achieve another astonishing double along with girlfriend Katie Boulter, who reached the semi-final of the Japan Open in Tokyo hours before his success in Vienna.

If they both lift titles in the same weekend, it would be the third time they’ve achieved the feat this season.

“She’s putting pressure on me because she’s playing before me,” smiled de Minaur after his win over Mensik.

“If it happens again, that’s way too good.”

De Minaur will now face Russian Karen Khachanov in Saturday’s (Sunday AEDT) semi-final, while rising British star Jack Draper will meet Italy’s Wimbledon semi-finalist Lorenzo Musetti in the other last-four duel.

Getting into the mix for an ATP Finals place after the hip injury that’s 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 Mensik.

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

“(Giving up) is definitely not what I do,” said de Minaur afterwards.

“Now it’s crunch time. Every match counts, every single point counts, so I’m going to do my best.

“I haven’t played enough tennis this year. I’ve been sidelined for a while, so I’ve got plenty of energy and plenty of fight in me. I’m going to make sure I give it my all every time I step out on court.”

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.

The turning point felt like an exhausting 31-shot rally early in the final set in which de Minaur outlasted the youngster. Seemingly deflated, Mensik lost the next five points en route to being broken.

– With AAP