Englishman Tom Lewis birdied five of the last seven holes to win his maiden title at the Portugal Masters, in only his third professional start in golf.
The 20-year-old, who shot to fame by leading The Open as an amateur in July, beat a field that included Padraig Harrington and Martin Kaymer.
Lewis, who entered the closing stretch only in seventh spot, shot a closing 65 to finish with a 21-under-par 267.
“If you said that I’d finish 21 under, I’d have said ‘no way’,” he said.
“I’m a long way behind Rory in the Order of Merit so I’ve got a long way to go. But I’m really pleased.
“To shoot 65 in the last round, I wouldn’t have thought I’d be able to do that.”
Spain’s Rafael Cabrera-Bello was the nearest challenger, finishing two shots adrift.
Tiger Woods needed five tournaments to land his first professional title, while McIlroy did not taste success until his 38th European Tour event.
Lewis two-putted the long 12th and then had four more birdies in a row from the 14th. He kept his nerve to par the dangerous final hole and had to wait the best part of an hour before victory was confirmed.
Instead of facing a trip to the Tour school in December – he entered the week 234th on the Tour money list and 621st in the world – he is now exempt for two seasons because of his win.