Italy’s Matteo Berrettini had to dig deep to beat Russia’s Andrey Rublev 7-5 7-6 (7-4) at the Vienna Open and set up a semi-final clash with top-seeded Austrian Dominic Thiem.

The win over the Kremlin Cup champion saw the third-seeded Berrettini reach his eighth semi this year and improved his chances of qualifying for next month’s season-ending ATP Finals.

Six spots have already been filled and the Italian, who is currently eighth in the Race to London rankings behind German Alexander Zverev, will qualify if he beats Thiem.

“I am really happy. It was a tough match, mentally and physically,” Berrettini said.

“Andrey is playing his best tennis so far. Last week, he won Moscow, so he was feeling confident and I saw it on the court.”

Berrettini won 80 per cent of his first serve points and converted a break point in the opening set — the only break in the match — to eliminate the 22-year-old.

Earlier, Spaniard Pablo Carreno Busta was forced to retire from his quarter-final match with Thiem leading 5-0 in the opening set, allowing the local favourite to move into the last four.

Russian second seed Karen Khachanov was beaten 7-6 (8-6) 6-2 by Argentine Diego Schwartzman, who was playing his 60th match of the year.

Khachanov served for the opening set at 5-4 but Schwartzman levelled and then went on to win a close tiebreak when the Russian double-faulted on set point.

Schwartzman broke in the opening game of the second set and again in the fifth before closing out the contest on his first match point.