What's at stake at the BMW Championship

— -- LAKE FOREST, Ill. -- It is the tournament within a tournament. This week's BMW Championship is plenty big on its own -- for golf history buffs, it is an extension of the Western Open, which dates to 1899 -- with an $8.75 million purse and $1,575,000 going to the winner.

But there is a prize beyond the prize, namely next week's Tour Championship and the opportunity to play for the $10 million FedEx Cup bonus that goes to the leader of a season-long points list.

The top 70 qualified to play at Conway Farms, where the BMW Championship begins Thursday and where they'll be vying for the 30 spots that will make up the Tour Championship field in Atlanta. The top 5 after this week are in position to win the FedEx Cup with a victory at East Lake.

In reality, the top 20 in FedEx Cup standings at this point are all but assured of advancing, and likely more than that. It means that really only about five to eight spots are up for grabs, as those near the bottom of the top 30 are looking to hang on while those outside know they need to make a move in order to keep playing next week.

With that in mind, here is a look at what is at stake for several players whose fate is not yet determined.

Rory McIlroy The defending FedEx Cup champion needs a big rally to have a shot at reclaiming the title, which has been elusive for the past 10 champions in playoff history. Only three of the previous nine winners of the FedEx Cup have made the top 30 the following year, and only Jordan Spieth (who won in 2015) finished in the top 10. ( Tiger Woods was out with injury in 2008 after winning the inaugural FedEx Cup.)

McIlroy, whose world ranking is No. 6, is ranked only 51st in FedEx Cup points this year and likely needs a top-4 finish here in order to advance to Atlanta. It has been a disappointing year on the course for McIlroy, who has not won amid two lengthy absences due to a rib injury. Throw in an equipment change plus a caddie change, and it would be no surprise if McIlroy is ready to get the year completed. He has said that after the playoffs, he'll play the Dunhill Links Championship on the European Tour and then shut it down for the rest of the year.

Jason Day It's hard to believe that Day has not won since his 2016 Players Championship victory. Back problems thwarted him toward the end of last year, and this year he's been dogged by mediocrity -- although he did lose in a playoff at the Byron Nelson Championship and he's shown some form of late, with two recent top-10s, including a tie for ninth at the PGA Championship.

His tie for sixth at the Northern Trust pushed him inside the top 30 in FedEx Cup points for the first time all year, and at 28th in the standings he can advance by finishing among the top 30 at Conway Farms -- where he won two years ago. How he will be impacted by a caddie change this week will be interesting to follow.

Ian Poulter The Englishman turned around his fortunes with a strong spring and summer, and now he has a chance to qualify for his first Tour Championship. He'll likely need a top-4 finish, but getting to Atlanta means more than just the monetary perks.

For several players battling it out this week, finishing among the top 30 means spots in the major championships for which they have yet to qualify. The Masters, U.S. Open and The Open all exempt the top 30 in FedEx Cup points. The PGA Championship uses a points system, and a top-30 finish goes a long way toward qualifying. Poulter, 47th in FedEx Cup points, missed the Masters and U.S. Open this year, so getting to Atlanta is a big deal.

Phil Mickelson Lefty doesn't have to worry about the major championships, but he'd love to make it to the Tour Championship, where he has played in eight of the previous 10 in the FedEx Cup era, winning at East Lake in 2009. A tie for sixth at the Dell Technologies Championship gave him the boost he had been looking for after a lackluster summer and helped him secure a captain's pick for the U.S. Presidents Cup team.

At 36th in the standings, Mickelson needs to finish no worse than 13th in order to advance.

Sergio Garcia The Masters victory in April undoubtedly makes this a great year for the Spaniard, who has seemingly played without much purpose since. He's teed it up only eight times around the world since his win at Augusta, and he missed the cut at the PGA Championship. He then skipped the first playoff event, making the task of getting to East Lake more difficult.

Ever since losing in a playoff at the Tour Championship nine years ago, Garcia has seemed indifferent about playing in Atlanta. At 34th in the standings, he needs to finish no worse than 18th at Conway Farms to have a chance.

Charles Howell III The Augusta, Georgia, native has played in his hometown Masters just twice since 2008, the last time coming in 2012. A top-30 finish obviously assures that, along with those coveted spots in the U.S. Open and The Open.

Howell could have taken care of that with a victory, but he lost in a playoff at the Quicken Loans National. He hasn't helped himself recently, finishing 62nd at the Northern Trust and missing the cut at the Dell Technologies Championship.

But he's still got a chance if he can pass at least five players this week. Howell is ranked 35th and needs at least a 13th-place finish to make it to Atlanta.