(Reuters) - The back-and-forth between Rory McIlroy and Jordan Spieth at the top of the world rankings shows no sign of slowing down with a further change possible after this week's BMW Championship in Lake Forest, Illinois.
Northern Irishman McIlroy returned to the summit when the latest rankings were issued on Monday, the fourth successive week that he and American Spieth have traded places.
The margin between the two is a wafer-thin 0.023 average points, the narrowest gap 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 playoff event of the season, and either of them -- along with third-ranked Australian Jason Day -- could be world number one next week.