Donald was quick to send his congratulations, crooning about his young friend's 'incredible year'. McIlroy has won his second major, three other coveted American events and taken the mantle of world No 1. Incredible, indeed.
After being pipped by Lee Westwood in 2009 and Donald in 2011, McIlroy had targeted the Race to Dubai. "It really is hugely satisfying to finally become the European No 1, especially after finishing second two of the last three years," said McIlroy, after becoming the Order of Merit's youngest winner since Sandy Lyle in 1980.
"Winning the USPGA already made it a fabulous season, but then to follow Luke Donald in becoming No 1 in both Europe and the States is the icing on the cake," McIlroy said. "I set myself a number of ambitious goals at the start of the year, and to have ticked so many of the boxes feels great." At just 23, he must be running out of boxes.
Sunday's six-under in Singapore was testament to McIlroy's quality as he made the required leap to third place outright to afford himself the luxury of playing in Hong Kong this week and then at the Dubai finale next week already guaranteed the £630,000 bonus. The monster putt of the par-five was to prove all important, with Thomas Bjorn finishing one behind in fourth.
McIlroy still had to wait to see whether Louis Oosthuizen could beat Manassero in a play-off and keep the money race alive in the minds of the mathematicians. But the young man from Verona also eagled the 18th, putting a 12-footer on the third sudden-death hole to deny the South African.
The champagne was well and truly off the ice, although, typically, McIlroy sought to downplay his achievement. "The money list has been cheapened a little bit by not having the leading players at events towards the end of the year," said McIlroy, who himself skipped last week's HSBC WGC Champions event. "It's still an award for consistency and you need to play well throughout the year in all the tournaments you attend.
"I am going to end up playing 13 or 14 events on the European Tour this year. That's obviously a lot less than a lot of other people but I have played in the bigger tournaments with the higher prize funds, which has allowed me to get to the top."
His outstanding talent has helped as well. When McIlroy comes to reflect on his career, he may think of 2012 as one of the most significant years. For now, however, he is keen to press on into 2013.
"I've got a healthy lead in the world rankings, but with so many very good players on both sides of the Atlantic this winter break will not be a time to be resting on my laurels," said McIlroy.
"Colin Montgomerie won eight Order of Merits and I have won one, so there is plenty of ground to make up. Also Jack Nicklaus won 18 majors and I now have my name on two, so targeting the majors will still be my main focus next season."
Of course, this was just as important a day for Manassero. Two years ago, he became the Tour's youngest-ever winner at 17, but an indifferent season had caused him to slip from 29th in the world to 85th. "It's been very frustrating at times," said the Italian, who shot a final-round 69 for a 13 under total. "I had to be more clear in my mind thinking that I started my career really well, but it's very early. I've got many years."
This was Manassero's third title and took his career earnings to more than £2.5million. Not bad for a teenager who believes he has endured a slump.