For the first time in his young golfing life, Rory McIlroy starts a tournament knowing that by the end of it he could be world number one.

That is the extra incentive for the 22-year-old Northern Irishman in the first of this season's world championships, the 64-man Accenture Match Play at Dove Mountain near Tucson.

McIlroy, who faces South African George Coetzee in the opening round, will go to the top of the rankings if he wins the title on Sunday and defending champion Luke Donald falls at the first or second hurdle.

Given that he starts against Ernie Els, a seven-time winner of the sport's other match play event in its days at Wentworth, Donald is taking nothing for granted.

His nine-month hold on the number one spot is also under threat from Lee Westwood, the man he took the crown off in a play-off last May.

Westwood, up against Belgian Nicolas Colsaerts, will regain the position with victory this weekend as long as Donald does not make the quarter-finals.

But the possibility of McIlroy reaching the summit three months before his 23rd birthday is a headline-grabbing development, even with Tiger Woods facing Spaniard Gonzalo Fernandez-Castano a year after Thomas Bjorn sent him packing at the same stage.

"The rankings are sort of a by-product of what you do," said McIlroy. "I'd rather just concentrate on trying to win tournaments and trying to improve as a player.

"If I happen to do that, then hopefully the ranking will take care of itself."