Star trio to renew rivalry at BMW

Chicago - Rory McIlroy knows his grip on golf's number one world ranking is tenuous at best, and there's just one way to keep Jordan Spieth and Jason Day at bay.

"It's just about playing well," McIlroy said as he prepared for Thursday's start of the BMW Championship, the penultimate event in the US PGA Tour's four-tournament FedEx Cup playoffs that will end with the Tour Championship.

McIlroy goes into the tournament at Conway Farms Golf Club with a narrow lead over Spieth atop the world rankings, having regained the summit on Monday even though neither played last week.

It was the fourth straight week that he and Spieth traded the top spot.

"It'll be like that until one of us separates ourselves a little bit," McIlroy said.

But Day has made it a three-horse race, and the Australian said his own week off had left him rested and ready for "crunch time" on the US PGA Tour.

"I feel refreshed, I feel good to go," said Day, who said fatigue contributed to mental errors that cost him a chance to contend at the Deutsche Bank Championship two weeks ago -- where he had his first crack at world number one.

Although he said gaining the summit would be "fantastic," Day and his rivals have plenty more to think about this week as they jockey for position going into the Tour Championship - where a $10 million bonus to the FedEx Cup series winner will be up for grabs.

"Just playing good golf and trying to win both tournaments," Day said of his mind-set going into the last two events of the US season - noting that Billy Horschel won the BMW and the Tour Championship to grab the bonus last year.

"Things like this can happen," Day said.

While Day endured a disappointing outing at the Deutsche Bank, Spieth is seeking an even bigger bounce-back after missing his second straight cut there.

The Masters and US Open champion, who like Day has four wins this season, said a turnaround is "just a matter of getting it rolling."

Despite his sudden struggles Spieth, like Day, is assured of making the 30-strong field for the Tour Championship with a top-five place in the playoff standings.

"It makes you feel like you may as well go for broke here, play some shots under pressure that are more dangerous," Spieth said.

American Rickie Fowler is also in a strong position in the playoff race after a one-stroke victory at TPC Boston two weeks ago.

"Just get off to a good solid start tomorrow and there's no reason why I can't be in a position to win the golf tournament come Sunday," Fowler said.