The muscular young man kissing the Wanamaker Trophy in the gathering gloom at Valhalla this month stood in total contrast to the skinny young teenager who competed in the inaugural Faldo Series at Fanling in January 2005.
The same beaming smile under a shock of black-brown curls was about all that remained, while the frame with which this talented and disciplined young man now unfurls his powerful golf swing is covered in thick layers of well-toned muscle.
McIlroy was just 15 when I met him on his first trip to Hong Kong, and where he finished third behind England's John Parry. He was pencil thin and his pale blue squad shirt seemed two sizes too big.
He went on to enjoy an incredible 12 months after he returned to Ireland by winning a host of international amateur titles, and that same year he fired an 11-under par course-record 61 in the second round of the North of Ireland Amateur Championship at Royal Port Rush, a course with more natural defences than a high-security prison.
McIlroy returned to Hong Kong a year later to try to win the Faldo Series title, and by this stage he was one of the world's best amateur players. He came up short once again as England's Ben Evans won the title under the watchful gaze of host Nick Faldo.
While photographing the practice round I was amazed at how far this skinny young kid could crush his drives - he had weapons-grade power even then. Once practice had finished I asked McIlroy if I could speak with him as a representative of SCMP.
We sat on the veranda of the Fanling clubhouse and chatted away for more than half an hour, while most of the other competitors toiled away on the practice putting green a few metres away.
I was immediately struck by how mature and articulate he was and how confidently he answered questions. He told me he did not plan to go to university and his sights were set firmly on a professional career.
When I asked him if he had been approached by any management companies he grinned and said: "Yes, but I'll be signing with Chubby [Chandler] when I do decide to turn pro. He's looked after Darren [Clarke] for many years, so I will be joining his team."
McIlroy said he was disappointed to have been left out of the previous year's Walker Cup team. He said he had accepted invitations to compete in two European Tour events, including the British Masters, which meant he missed out on competing in a couple of top amateur events.
"I thought I would get picked for the team if I placed in the top-20 in a European Tour event rather than by winning an amateur event," McIlroy said. Unfortunately the gamble failed as he missed the cut by a margin in the Masters. "I got caught up in the moment," he said of his first ever start in a pro tournament.
McIlroy's total confidence in his ability to compete at the highest level was evident even back then. Most amateur players would have considered making the cut in a pro event to be a huge success, however the young Northern Irishman had genuinely aimed at a top-20 finish.
Eager to compete in the Walker Cup, McIlroy said he would remain an amateur until the 2007 event.
"The Walker Cup will be played at Royal County Down, and I really want to be on the team as the club is just down the road from where I live - I've played the course so many times over the years," he said.
McIlroy was picked for the GB & Ireland team and found himself facing players who would also rise to the top of the pro game, including Rickie Fowler and Dustin Johnson. The US team won the trophy by just one point, and McIlroy turned pro right after the event, aged 17.
I was working at the Dubai Desert Classic in 2008 when I saw McIlroy's name on the draw sheet. He had received a sponsor's invitation, and his father, Gerry, caddied for him.
McIlroy, now a professional, played in an afternoon flight and shot an impressive 69. He then had an early tee time on Friday morning for the second round. Tiger Woods was also playing and was in the other half of the draw, which meant he was playing on Friday afternoon.
I was photographing the final few groups during the afternoon when I caught sight of McIlroy in the packed gallery. For some strange reason he was walking around carrying a five iron. Not being particularly tall he was struggling to see over the heads of the mostly expat gallery.
I asked him how he had played but he was a bit subdued. "I shot 77 to finish on two over par, I'm not sure whether that will be good enough to make the cut or not," he said (he missed by one).
As the Woods group made their way down the 14th fairway the gallery quickly swelled, so I suggested to McIlroy that he should come under the rope and "help" me carry one of my cameras.
Only players, officials and accredited media are allowed inside the ropes, but as the youngster had been playing inside the ropes for two straight days he ought to enjoy a slightly higher status than the rest of the gallery.
McIlroy walked with me for the final five holes while I photographed the Woods group and as the mesmerised young man watched his idol in action from close quarters it was evident McIlroy was fascinated by what he saw that day (Woods went on to win the title).
One year later I was standing in the rough on the 10th hole of the same golf course at the same tournament when McIlroy came walking up the fairway to play his second shot.
After he played his shot on this long par five, he walked over and shook my hand and asked how I was. The boy had become a man, in golf terms, anyway. By now he was adorned with sponsors branding and looked very much the part. Three days later, aged just 19, he recorded a one-shot victory over Justin Rose to claim his first professional title.
The curls that used to sit inside his cap were now bulging over his ears and even had blonde streaks. Despite his day job he was still doing the experimental things that teenagers do when they think they have finally grown into an adult.
After the final round and the obligatory interview in the media centre, an ecstatic McIlroy walked past my desk as I was editing photos of the prize presentation ceremony. He looked at the images on my laptop with a deep sense of pride. I asked him if he would like me to send him some copies, and so he gave me his email address.
McIlroy's affiliation with Hong Kong was rekindled after he turned pro, and he returned to play in the 2008 Hong Kong Open where he lost in a play-off to Taiwan's Lin Wen-tang. His second-place finish to Frenchman Gregory Bourdy the following year simply made him determined to come back and try again.
After finishing sixth behind Ian Poulter the following year he finally claimed the title in 2011, and his delight at holing a bunker shot on the 72nd green was evident for all to see.
What the rest of us didn't know was that he was actually trying to hole that bunker shot - there was no luck involved. His quest for perfection knows no bounds.
I never thought to ask him but was curious as to whether he continued to return to Hong Kong to try to avenge his early losses in the Faldo Series. When he has an itch he scratches it.
By this stage in his career McIlroy had the obligatory managers and minders to shepherd him when he was off the golf course, but we often chatted during practice rounds and pro-ams before the tournament started.
He told me he enjoyed visiting Hong Kong because it is such a vibrant city, and he also said he enjoyed the challenge of the Fanling course.
The managers have come and gone with alarming regularity, but the pay cheques have rolled in with more noughts than the US national debt.
Such wealth has brought with it an even higher level of security, and the days when McIlroy would hang around the clubhouse or go out to watch others play are long since gone, but being a well brought-up young man he still gives me a wave or a nod of recognition when we see each other at tournaments.
Long may it continue.