Poston tied Henrik Stenson's two-year-old tournament record at 22-under 258.

The native North Carolinian began his round three strokes back, took the lead for good with a birdie on the par-5 15th hole, then finished with three straight pars to earn US$1.1 million (AU$1.7 million) and 500 FedEx Cup points at the regular-season finale.

Webb Simpson was at 21 under after a 65. Byeong Hun An, who held or shared the lead after each of the first three rounds, three-putted the 18th for a bogey and a 67 to finish two shots back.

Trying to force a playoff with a birdie, he nearly holed a 60-footer but had it run well past.

Poston, who became the first player since Lee Trevino in 1974 to win a 72-hole stroke-play event on Tour without any bogies or worse, closed the gap with third-round leader An with three birdies and an eagle on the front nine.

RIGHT: Kizzire played his way into The Northern Trust by finishing T13th at the Sedgefield. PHOTO: Jared C. Tilton/Getty Images.

Then came the 15th when Poston took sole possession of the lead with a birdie after placing a bunker shot six feet from the flagstick.

An, playing two groups behind Poston, sent his tee shot on that hole into the weeds. He took a penalty stroke, then landed his third shot left of the green, left his chip 35 feet short and dropped to 20 under after two-putting for his first bogey of the tournament.

After a birdie on the next hole and a par on 17, An needed to finish with a birdie to force a playoff. He sent his tee shot into the trees and recovered by landing his second shot 60 feet from the pin.

The annual subplot at Sedgefield focused on the players on the playoff bubble.

Two players who began the tournament outside the top 125 – No.129 Patton Kizzire and No.134 Andrew Landry – played their way into the field for The Northern Trust next week in New Jersey.

"I definitely knew what I was playing for," Kizzire said.

Cameron Davis was the only Australian to make the cut and his final round 65 saw him jump 16 places to finish in a tie for 22nd.