Former world number one Rory McIlroy needs a top-four finish in the BMW Championship to make certain of having a chance of retaining his FedEx Cup title.

McIlroy enters the penultimate play-off event at his lowest world ranking for more than three years, a missed cut in the Dell Technologies Championship seeing him slip from fourth to sixth in the standings behind US PGA champion Justin Thomas and Spain's Jon Rahm.

And crucially his position of 51st in the FedEx Cup standings means the 28-year-old needs to rediscover his top form at Conway Farms to climb into the top 30 and qualify for the Tour Championship in Atlanta.

The four-time major winner defeated Ryan Moore and Kevin Chappell in a play-off at East Lake 12 months ago to win the overall FedEx Cup title and 10million US dollars bonus and is keen to avoid just a second full winless season since turning professional.

The Northern Irishman is due to contest the Alfred Dunhill Links Championship with his father Gerry from October 5-8 before calling time on an injury-hit campaign which has seen him restricted to 15 events.

In contrast, FedEx Cup leader Jordan Spieth has played 20 tournaments, winning three - one of which was the Open at Royal Birkdale - and recording three runners-up finishes, including both play-off events to date.

But the former world number one admits motivation could be an issue this week as his place in the top five heading into Atlanta is already secure, even with the points being reset after Sunday. Anyone in the top five who wins the Tour Championship will win the FedEx Cup title, regardless of other results.

"In the position I'm in now that's certainly a good question," Spieth told a pre-tournament press conference. "I was struggling a little with that going into New York (the first play-off event), finding motivation after the major season and a lot that happened for me late in the summer.

"These play-offs, if you're in a very good position going in and feel like you're playing well the first three can seem a little more difficult because you can see the light at the end of the tunnel - you know that East Lake is really what matters in the way that these points work.

"The way it used to be, if you could win the FedEx Cup before going to East Lake like Vijay (Singh) did that one year, it's a totally different scenario.

"But when everything gets knocked back down anyways, you're playing a PGA Tour event while focused on the next one."

Conway Farms has hosted the BMW Championship twice before, with Zach Johnson winning in 2013 and Jason Day easing to a commanding six-shot victory in 2015.

However, Day will try to win the event for a second time without his mentor and coach Colin Swatton acting as his caddie, the former world number resting Swatton in favour of his close friend Luke Reardon.

It is understood that Day has given Reardon a trial period until the end of the season. The Australian is 28th in the FedEx Cup and is likely to need a top-30 finish in Chicago to qualify for East Lake.