Justin Thomas holds aloft the winner's trophy at the Dell Technologies Championship. Photo: @PGATOUR via Twitter

Justin Thomas rode a couple of lucky breaks to become the first five-time champion on the PGA Tour this season when he won the Dell Technologies Championship in Massachusetts on Monday.

Thomas emerged from a three-way tussle to beat fellow American Jordan Spieth by three strokes at TPC Boston in Norton, with Australian Marc Leishman another shot back in third place.

Thomas carded 66 to finish at 17-under-par 267, while Spieth bogeyed the par-five 18th to shoot 67.

Leishman, who led by two shots with nine holes left, faded with a 70, going out in 30 and coming home in 40.

Leishman bogeyed the last, which allowed Spieth to take the lead in the FedExCup standings, narrowly ahead of Thomas with two tournaments left in the four-event playoff series.

Thomas said it was the first time he had won without having his “best stuff”, and downplayed any notion that his victory would reverberate around the tour.

“I wasn’t trying to send a statement,” he told Golf Channel. “I was just trying to win a golf tournament.”

Thomas, 24, clinched his first major title at the PGA Championship last month, coming from behind over the final nine holes.

He followed a similar route to victory on Monday, this time with some help.

Thomas struck a tree with his tee shot at the par-four 10th hole, but had an unobstructed view of the green with his second shot and made an easy par.

Later, after a poor tee shot at the par-three 16th, he received a free drop from a poor lie in heavy rough, because a sprinkler head interfered with his stance. He was able to place his ball in a much better lie and got up and down to save par. That proved to be his last nervous moment.

Open Championship winner Spieth, meanwhile, licked his wounds after a second consecutive runner-up finish. He lost to Dustin Johnson last week at the Northern Trust in the first playoff event.

Spieth, three months younger than Thomas, observed that his good friend and rival had taken a couple of years longer to start fulfilling his talent.

“Jealous isn’t the word, but he probably had some feelings of anxiousness,” Spieth, who won two majors in 2015, told reporters. “I feel like we’re very similar calibre of player, and I just got a headstart. Obviously he’s become a tremendous closer.

“It’s tough when you’ve got somebody that’s that good and hot, and starts the day two shots in front of you.”

After a one-week break in the schedule, the top 70 players in the standings will contest the penultimate event of the season, the BMW Championship, outside Chicago.