LOS ANGELES • The back and forth between Rory McIlroy and Jordan Spieth at the top of golf's world rankings shows no sign of slowing down, with a further change possible after this week's BMW Championship in Lake Forest in Illinois.
Northern Irishman McIlroy returned to the summit when the latest rankings were issued on Monday. It is the fourth successive week that he and his American rival have traded places.
The margin between the two is a wafer-thin 0.023 average point, the narrowest between the world's top two players since the official rankings were launched in 1986.
McIlroy and Spieth are both in the field for the BMW Championship, the penultimate FedExCup play-off event of the season.
Either of them - along with third-ranked Australian Jason Day - could be world No. 1 next week.
"It'll be like that until one of us separates ourselves a little bit," McIlroy said ahead of tomorrow's opening round at Conway Farms Golf Club in Lake Forest.
"At the end of the day, it's just about playing and playing well.
"I don't know any other way we could determine the best player in the world.
"You could do it on a one-year point system instead of two.
"I think two years is a good reflection of how you played."
The ranking system is structured on a two-year "rolling" period with points awarded for each event.
It is then maintained for a 13-week spell to give additional emphasis on recent performances.
Ranking points are then reduced in equal decrements for the remaining 91 weeks of the two-year time frame.
"We're all focused on our own goals," said Masters and US Open champion Spieth.
He became world No. 1 for the first time after finishing runner-up to the triumphant Day in the PGA Championship at Whistling Straits last month.
"As one, two and three in the world, we're the three who have to beat each other at the top right now in order to try to get to the top, or to remain at the top.
"I'm not focused on what either one's doing on the leader board unless they're in the lead, and then if they're in the lead, how do I get up there and surpass them?"
The only previous time when there were changes at the top of the rankings for four successive weeks was in June 1997.
Then, Greg Norman, Tiger Woods, Ernie Els and then Norman again exchanged places.
Day 1 (StarHub Ch204, Friday, 3am)