CARMEL, Ind. -- Marc Leishman remembers the nervous feeling as he stood over a short putt on the final hole of the BMW Championship. It was his first time in the FedEx Cup, and the stakes were so enormous that he had a hard time blocking out everything but getting the ball in the cup.

The $10 million bonus? No, that was still a week away.

"I was thinking to myself, 'Hole this putt and you're in the Masters.' I wasn't thinking about $10 million," Leishman said. "To get into the Tour Championship ... look, the money is awesome, but everything that came with it was better."

That's what makes the BMW Championship, which starts Thursday at Crooked Stick, the most important playoff event in the FedEx Cup.

Only the top 30 from the 70-man field advance to the Tour Championship, and they are exempt for the Masters, U.S. Open and British Open. That might not be a big deal to Tiger Woods or Rory McIlroy. But it means everything to players like Leishman, who had never played a major in his life until a tie for second at the 2009 BMW Championship got him into all four of them.

Anyone who plays in the Tour Championship has a mathematical shot at $10 million because the points are reset. The higher a player is on the list, the better the odds. The top five are guaranteed the big bonus simply by winning at East Lake, although everyone in the field now has reason to believe it could be them. A year ago, Bill Haas was No. 25 when a curious

McIlroy, firmly established now as No. 1 in the world after his win last week on the TPC Boston, is No. 1 in the FedEx Cup standings. He's followed by Barclays winner Nick Watney, Woods, Ryder Cup pick Brandt Snedeker and Louis Oosthuizen.

Far more compelling are the players trying to crack the top 30.

Jimmy Walker, for example, is at No. 46. He has never played in the Masters, the U.S. Open or the British Open. He is four good rounds from moving into the top 30 and getting into all three of those majors next year.