Rory McIlroy has won four major titles and spent 122 weeks as the world's No. 1 golfer - but he had his doubts about a rival who went on to become the top-ranked player

With a glittering junior pedigree and a PGA Tour win at the age of 19, Spieth was one of the most hyped-up youngsters of his generation. But McIlroy was not overly impressed after first getting the chance to watch him at close quarters more than a decade ago.