MARC Leishman has settled for third at the US PGA Tour's second playoffs event, behind winner Justin Thomas and world No.2 Jordan Spieth.
The Australian led heading into the final round in Boston but delivered five back-nine bogeys to card a one-under 70 at TPC Boston to finish the tournament at 13-under.
He had earlier claimed a two-shot lead with six birdies.
A win would have seen Leishman well placed for the $US10 million bonus that is handed to the winner of the season-long points race after the fourth and final playoffs event, the 30-man Tour Championship.
Still, his third placing lifts Leishman from 20th to seventh in the standings.
The Victorian is enjoying his best US tour season after winning the Arnold Palmer Invitational in March.
Thomas, the most recent major champion after winning the PGA Championship, claimed victory after a five-under final round took him to 17-under.
Spieth finished three strokes back with a four-under 67 final round.
Spaniard John Rahm and Briton Paul Casey were a shot behind Leishman in a tie for fourth.
Australian world No.9 Jason Day finished strongly after eight birdies, closing his round with three bogeys to shoot 66 and finish at six-under, and a tie for 25th.