BASEL, SWITZERLAND (Reuters) - Croatian wunderkind Borna Coric produced more emphatic proof of his potential when he beat 14-times grand slam champion Rafa Nadal in the quarter-finals of the Swiss Indoor tournament on Friday.

The 17-year-old, already being called 'Baby Djokovic' because of similarities with world number one Novak Djokovic, gave an off-colour Nadal a torrid time, winning 6-2 7-6 (4).

The Spaniard, who is suffering from appendicitis and earlier in the day pulled out of next week's Paris Masters, was unrecognisable in the first set as he offered no resistance.

Nadal's timing improved marginally in the second but twice Coric served to stay in the set and held his nerve when a loose forehand from his opponent gave him two match points.

Coric needed only one of them, forcing a weary Nadal to send a defensive forehand wide.