The 25-year-old, currently ninth in the ATP Live Race To Turin, dug deep and emerged victorious in two hours and 34 minutes.

Mensik was the first to switch gears as the opening set went into a tie-break. He employed aggressive groundstrokes and forced errors from the Australian to claim the first set 7-6(2). He fired 24 winners in the first set, including nine aces, according to the ATP stats.

De Minaur responded by earning a crucial break in the sixth game of the second set and levelled the match by clinching the set 6-3. The Australian broke Mensik again in the fifth game of the third set and stayed in control for the rest of the match.

Despite the loss, Mensik remains on track to qualify for the Next Gen ATP Finals in December. The 19-year-old is third in the ATP Live Race To Jeddah.

Elsewhere, Khachanov defeated Matteo Berrettini 6-1, 6-4, and extended his winning streak to seven matches.

The 28-year-old, who won the Almaty Open last week, dispatched the Italian in one hour and 18 minutes to reach his first semi-final at the ATP 500 tournament in Vienna.

With the win, Khachanov registered his first victory in the pair’s ATP Head-to-Head Series, which Berrettini leads 4-1.