ATLANTA (Reuters) - Little-known American Scott Piercy stunningly overcome the odds to earn a cheque for $2 million (1 million pounds) five years ago but he knows his chances of landing FedExCup honours at the Tour Championship are slim at best.

Scott Piercy of the U.S. (R) reads the 17th green with caddie Darren Woolard before posting a 3-under-par first round score in the Tour Championship golf tournament at the East Lake Golf Club in Atlanta, Georgia September 20, 2012. REUTERS/David Tulis

Piercy came into this week's event occupying the 30th and final spot in the FedExCup points standings and for him to clinch the playoff title and its staggering bonus of $10 million, plenty would have to go his way.

Though he rocketed into contention by firing a three-under-par 67 in Thursday's opening round, he would need points leader Rory McIlroy to end the week no better than 30th in the elite field of 30, along several other scenarios.

"My chances are slim to none," Piercy told reporters after marring a good start at East Lake Golf Club with a double-bogey at the par-three last. "I think Slim's about to leave the building.

"McIlroy has to finish 29th or worse ... and Tiger would have to finish outside the top five. There are too many good guys up there that I think just block me out, even if I win (the Tour Championship).

"That's why I'm trying to take the positives. If I win here, I finish second (in the FedExCup). It's still a million and a half (dollars) for first place, and another $3 million for the FedEx, so I'll take $4.5 million. That would be sweet."

In 2007, Piercy hit the jackpot with a $2 million pay-day when he birdied five of the last six holes to triumph at the made-for-television, winner-take-all Ultimate Game tournament in his hometown of Las Vegas.

He has since gone on to record two victories on the PGA Tour, most recently at the Canadian Open in July, and is delighted to be contending for the fourth and final playoff event on the U.S. circuit.

"It's definitely big for me to be here," the 33-year-old American said. "Getting the doors it opens, and just being part of 30 guys from the whole tour, I think it says a lot to where my game has come from.

"I think it's just a stepping stone in the process. I'm just really excited to be here."

Piercy recorded six birdies and one bogey in the first 16 holes to briefly lead the 30-man field by two strokes before he stumbled at the 18th.

"Seventeen and 18 are good holes and I made par and then kind of messed up on 18," he said. "But overall, I'm excited. I played solid. My thought was, try to win (the Tour Championship) this week, and get second (in the FedExCup).

"I think that's a realistic goal. If I play well, I think I have a good shot."

Piercy's prospects of winning the Tour Championship looked less likely once Thursday's opening was over with Woods carding a 66 and McIlroy a 69.

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