Australian men’s No.1 Alex de Minaur has powered his way into the semi-finals of the Swiss Indoors to continue his excellent finish to the 2019 tennis season.

De Minuar, who is guaranteed to climb to a career-high 22nd in the world rankings next week, beat big-serving German Jan-Lennard Struff 6-4 7-6 (7-4) to set up a semi-final against giant American Reilly Opelka.

Former Junior Wimbledon champion Opelka, who stands at 2.11m, hurled down 31 aces on his way to defeating Spanish world No.10 Roberto Bautista-Agut 7-6 (7-4) 6-7 (7-4) 7-5.

It was Opelka’s second big scalp of the week after he saw off world No.13 David Goffin in the round-of-16 on Thursday.

The much-anticipated all-Swiss battle between Roger Federer and Stan Warwrinka never materialised after the three-time grand slam winner was forced to pull out of the tournament due to a back injury.

“The disappointment is huge,” admitted Wawrinka.

“Not to be able to play this match in Switzerland is very sad. But I need to listen to my body at this point.”

Top seed and defending champion Federer is looking to win the tournament for a 10th time.

Federer will now play Greek world No.7 Stefanos Tsitsipas or Serbia’s Filip Krajinovic for a place in the final.