Shanghai - Justin Rose has set his sights on a career-high ranking of world number two over the final events of the year as he headlines a weakened field at the from Thursday.
The Englishman can further his claims in Shanghai after fifth-ranked Henrik Stenson pulled out, joining world number one McIlroy on the sidelines.
But Rose believes it might be a step too far to close the gap on McIlroy, who also leads the Race to Dubai, over the European Tour's "Final Series" of four big-money events.
"I'm not sure I can catch Rory, I haven't really done the maths 100 percent," Rose told AFP at Lake Malaren Golf Club on Wednesday.
"The aim is to strengthen my world ranking as much as possible. If I was to play well and win a few tournaments before the end of the season I could get myself to second place in the world rankings which would be a personal best."
McIlroy is taking time out to prepare for a multi-million dollar lawsuit with his former management company, and will not play again until the season-ending DP World Tour Championship in Dubai next month.
The Northern Irishman, who has won two majors this year, holds a healthy lead of more than three million euros in prize money at the top of the Race to Dubai standings.
The final series also includes next week's World Golf Championships HSBC Champions in Shanghai, the Turkish Airlines Open and the climax to the season in Dubai.
With the euros on the standings now converted to points, and each tournament offering 1,166,000 points to the winner, it means this year's battle to succeed Stenson, the reigning Race to Dubai champion, may not quite be over.
The BMW Masters has suffered a double blow with the withdrawals of McIlroy and Stenson after the Swede's wife, Emma, gave birth to their third child, on Sunday.
With world number four Sergio Garcia in Malaysia this week for the PGA Tour's CIMB Classic, it means the top three in the "Race to Dubai" standings are missing.
And that has opened the door slightly for the likes of fourth-placed Jamie Donaldson, Thomas Bjorn (fifth), Victor Dubuisson (sixth) and Rose (eighth) who are all part of this week's elite 78-man field.
Rose, a father of two himself, had sympathy for Stenson after he withdrew on Sunday.
"The six months of fall-out leaving your wife after just having a baby? It's not worth it," Rose said, smiling. "He's made the right decision."
The tournament was won last year by Gonzalo Fernandez-Castagno who has endured a torrid 12 months since.
The Spaniard had to rely on a sponsor's invite to defend his title, having dropped to 86th on the Race to Dubai standings.
And he now needs a high-placed finish here or his season will be over as only the top 60 in the standings will qualify for Dubai.
"For some reason I play well in China," Fernandez-Castagno told AFP, recalling last year's win and also his 2006 Asian Open victory across the city at Tomson Golf Club.
"Maybe it's the food or maybe it's being so far from Europe that nobody can bother me with phone calls and text messages," he said.
"I can just go out there and play."