But it was only when 19-year-old Italian Matteo Manassero also eagled the same hole more than two hours later that McIlroy could crack open the champagne again.
Already with the PGA Tour title in the bag, the 23-year-old world number one emulated the double achieved by Luke Donald last season when Manassero beat South African Louis Oosthuizen with a 12-foot putt at the third play-off hole.
If Oosthuizen had won he could still have caught McIlroy, but instead Manassero became the first player to win three times on the circuit before the age of 20. Not even Seve Ballesteros managed that.
McIlroy, watched during the week by girlfriend Caroline Wozniacki, stormed through to third place with a closing six-under-par 65.
"I left myself a little bit too much to do to win, but it was a great way to finish off the round and the tournament," said the Northern Irish star, who still has his defence of the Hong Kong Open and the DP World Tour Championship in Dubai to come this next fortnight.
The race would still have been alive if either Peter Hanson or Oosthuizen had played in Hong Kong or at this week's South African Open, but they have not entered.
Latest leading positions in the European Tour "Race to Dubai" money list after the Barclays Singapore Open:
1 Rory McIlroy £2,966,985, 2 Peter Hanson £2,120,959, 3 Justin Rose £2,059,798, 4 Louis Oosthuizen £2,044,184, 5 Ian Poulter £1,822,644, 6 Branden Grace £1,671,036, 7 Francesco Molinari £1,630,171, 8 Luke Donald £1,475,622, 9 Graeme McDowell £1,462,726, 10 Paul Lawrie £1,425,216
11 Nicolas Colsaerts £1,363,063, 12 Lee Westwood £1,317,982, 13 Matteo Manassero £1,198,873, 14 Marcel Siem £1,070,584, 15 Thorbjorn Olesen £995,685, 16 David Lynn £952,025, 17 Rafa Cabrera Bello £939,767, 18 Bernd Wiesberger £822,449, 19 Jamie Donaldson £815,188, 20 Alex Noren £805,292.