Cameron Smith has squandered a chance to win the Dell Technologies Championship in Boston but has cemented his status as Australia's best hope to finally win the $US10 million ($A13.9 million) FedExCup title.

For consecutive tournaments, 25-year-old Smith finished third behind in-form Bryson DeChambeau as the American cruised to his second play-offs victory in as many starts.

DeChambeau fired a four-under-par 67 for a 16-under total and a two-shot win from Englishman Justin Rose (68) at TPC Boston - becoming just the second player in the 12-year history of the playoffs to win the opening two events.

Smith carded a 69 to finish at 13 under, making another leap on the world golf rankings to No.32.

The Brisbane native was up against it on Monday with DeChambeau a group behind and in cruise control.

Smith made a pair of late birdies but was blindsided when his drive on the 72nd hole ran through the fairway and into a poor lie in the rough.

He then chunked his second shot into the hazard and carded a bogey on the par-5 18th.

DeChambeau said his TPC Boston win, which netted him another $US1.62m ($A2.25m) winner's cheque, was more difficult than duelling Smith in New Jersey last week.

"Honestly, down the stretch was a lot more difficult," he said.

"I saw Cameron making a run and unfortunately, he didn't finish out the way I thought he would; but it was fortunate for me."

The consolation prize for Smith is eight place on the FedExCup standings, now the top Australian.

If he posts a high finish at this week's BMW Championship in Philadelphia he could move into the top-five seeds for the Tour Championship finale in Atlanta.

The top-five seeds can guarantee the lucrative FedEx Cup bonus if they win the Tour Championship in Atlanta later this month.

No Australian has won the FedExCup title.

Jason Day, who owns two US Tour wins this year, missed the cut in Boston and dropped to 10th on the standings.

Marc Leishman (71) tied for 21st at eight under and moved up two spots to 22nd, while Adam Scott fired a blistering 66 to share 49th at three under.

Scott rounds out the Australian contingent in the $US67m ($A93m) finals series but dropped eight spots to 48th on the standings.