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

Nadal, who struggled with appendicitis this month 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 (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 made 19 unforced errors in the first set, before recovering somewhat in the second, but Coric — ranked 122nd in the world — matched him shot for shot.

Coric next faces David Goffin after the Belgian beat fourth-seeded Milos Raonic of Canada 6-7 (3), 6-3, 6-4.