Australian men's No.1 Alex de Minaur has powered his way into the semi-finals of the Swiss Indoors and guaranteed himself a new career-high world ranking to continue his excellent finish to the 2019 tennis season.

De Minaur - who will rise at least six places to reach a minimum of No.22 in the rankings next week, depending on how far he goes in Basel - 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 and he will now meet De Minaur, who has taken full advantage of the wildcard given to him by tournament organisers.