McIlroy did not play the BMW Masters and would have been overtaken by Danny Willett if the Englishman had finished alone in 28th or better in Shanghai.
However, a final round of 70 at Lake Malaren left Willett in a tie for 28th with two other players as he looks to finish the year as European number one for the first time.
A total of seven players can still win the Race to Dubai, although Justin Rose, Shane Lowry, Louis Oosthuizen and Branden Grace need to finish second or better at Jumeirah Golf Estates, while Byeong Hun An has to be first.
“Last week was pretty stale – obviously I had a good last round – and this week’s just been stale again,” said Willett, who carded a closing 62 to finish third in the HSBC Champions.
McIlroy has held top spot since finishing fourth in the Masters in April, pulling clear of the pack with victory in the WGC-Cadillac Match Play three weeks later.
With the four-time major winner out of action in the summer due to injury, Willett closed the gap with a tie for sixth in the Open at St Andrews and his second win of the season a week later in the Omega European Masters.
McIlroy will be confident of holding on to top spot given his record in the season-ending event, the 26-year-old finishing in the top five in five of his six appearances, winning in 2012 and second behind Henrik Stenson last year.