Teenager Borna Coric upset second-seeded Rafael Nadal in straight sets on Friday to reach the semi-finals of the Swiss Indoors and announce himself as one of the rising stars of tennis.

Nadal, who announced after the match he will have season-ending appendicitis surgery and was playing just his third tournament since Wimbledon due to a wrist injury, looked nowhere near his best while Coric was in sparkling form to win 6-2 7-6 (7-4).

It took the 17-year-old Croatian just 35 minutes to take the opening set, after storming into a 5-0 lead to stun the crowd.

Nadal, who made 19 unforced errors in the first set, rallied briefly and broke Coric’s serve before holding to love.

The Spaniard recovered somewhat in the second set, but Coric – ranked 124th in the world – matched his illustrious opponent shot for shot during some long rallies that had the crowd cheering in delight.

Both saved a break point apiece to force the set into a tiebreaker. Coric racked up two match points but needed just one to seal the greatest win of his short career.

Nadal needed treatment for appendicitis this month in Shanghai and said he will have surgery on November 3, ruling him out of next week’s Paris Masters and the season-ending ATP finals in London.

Coric next faces David Goffin after the Belgian kept up his remarkable form to beat fourth-seeded Milos Raonic of Canada 6-7 (3) 6-3 6-4.

Top-seeded Roger Federer or Grigor Dimitrov will play Ivo Karlovic in the other semi-final after the eighth-seeded Croatian beat Benjamin Becker 6-4 6-4.

It was Goffin’s 42nd victory in 44 matches since his straight-sets loss to Andy Murray at Wimbledon, and the first time the 23-year-old Belgian has beaten a top-10 player.

“It’s one of my nicest victories, if not the nicest,” the seventh-seeded Goffin said.

“I can’t really comprehend what I’ve achieved since Wimbledon: more than 40 victories, two titles … I think I’ll only realise what I’ve achieved when I’m on holiday.”