Horschel claims FedEx Cup

American Billy Horschel has claimed a mammoth payday after taking out the US PGA Tour Championship and the season-long FedEx Cup.

Horschel, who won last week at the BMW Championship, added another two trophies at East Lake Golf Club while putting a hefty increase in his bank balance.

A final round two-under 68 left the 27-year-old at 11 under par for the week, three clear of his nearest challengers in world No.1 Rory McIlroy (71) and American veteran Jim Furyk (69), who finished eight under.

By adding the $US1,440,000 ($A1.56 million) winners cheque from East Lake and the $US10 million ($A10.82 million) bonus for being the FedEx Cup season-long points leader, Horschel walks away with $US13,477,333.33 ($A14.58 million) for his last three weeks of work.

Australian Jason Day (69) joined Justin Rose (69) and Chris Kirk (68) in a tie for fourth at seven under.

McIlroy, co-leader with Horschel overnight, went into the final round as favourite but after relinquishing his share of the lead on the fifth hole he dumped his tee ball in the water on the par three sixth and took a double bogey, making his claim for the big money an uphill battle.

Furyk was within one with two holes to play but finished with two bogies to end his charge.

Day, who started just three back and was within two of the lead early, faded in the middle of the round before two late birdies ensured a high finish.

World No.2 Adam Scott (70) finished in a tie for ninth at four under.

John Senden ended the event with a four-over 74 to be 10 over for the week and 26th while Geoff Ogilvy (73) finished last in the 29-man field at 20-over.

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