Thomas, who entered the final round Sunday three strokes behind the leader, won his 14th career title on the PGA Tour.
PONTE VEDRA BEACH, Fla. — It was evident early that the final round of the Players Championship might not unfold as expected when Bryson DeChambeau took one of his trademark mighty swipes and barely made contact with the top of his golf ball, which nose-dived and skittered into a pond roughly 100 yards away.
Next, on the same tee, was Lee Westwood, who was leading the tournament and predicted to duel DeChambeau, who was in second place after the first three rounds, throughout Sunday afternoon. Westwood hit a slice so crooked it would have warmed the heart of the everyday hacker. Westwood’s ball plunked into a different pond than DeChambeau’s, but the tone for the day was undeniably cast.
Playing in the pairing ahead of DeChambeau and Westwood, Justin Thomas was not aware of the travails going on behind him. But he had a studied understanding.
“I’ve watched this tournament for years,” Thomas said, “and I know lots of crazy things can happen.”
Thomas began the last round three strokes behind Westwood but passed him, and DeChambeau, to take the tournament lead with an eagle on the 11th hole. From there, as his rivals wobbled, he was steady, especially when he birdied the 16th and made gritty pars on the two treacherous closing holes at the TPC-Sawgrass course.
On a day of unforeseen ups and downs, Thomas’s consistency led to a one-stroke victory and another noteworthy title, his 14th on the PGA Tour. Thomas, 27, has also won a P.G.A. Championship and the 2017 FedEx Cup playoffs.
“I was bold when I had to be — I took risks,” Thomas, who finished the tournament at 14-under par, said afterward. “But I was also patient when things didn’t go exactly as planned because you knew it was going to be that type of day.”
The victory also was a respite in a stormy year for Thomas, the second ranked golfer in the world.
In January, a television boom microphone caught him muttering a homophobic slur to himself after a short missed putt at the Sony Open. Thomas apologized immediately and has not shied from the consequences, which included a social media outcry and the loss of his clothing sponsor.
In February, his 89-year-old paternal grandfather, Paul, a P.G.A. professional with whom Thomas talked daily, died. Later that month, Tiger Woods, who has become one of Thomas’s closest friends, was seriously injured in a car crash.
Since the crash, Thomas has stayed in almost daily contact with Woods, including on Sunday when Woods wished Thomas luck before the final round. In his last four tournaments this year, Thomas had seemed distracted and turned in poor results, especially for a player of his recent pedigree.
“It’s been a bad couple of months,” Thomas said after Sunday’s victory. He added: “I told my family I’m ready for something good to happen this year. I’d say this qualifies.”
Thomas was in danger of missing the cut with nine holes remaining in his second round on Friday, but he rallied with four birdies on the back nine to earn a spot in the last two rounds. He began Sunday with seven consecutive pars on a warm but mostly windless day in northeast Florida. Though the conditions were benign, they still did not lead to many low scores on the devilish Pete Dye-designed layout. Thomas, whose closing 36-hole score of 12 under par was a tournament record, vaulted to the top of the leaderboard with birdies on the ninth, 10th and 12th holes — along with his eagle on the par-5 11th hole.
With DeChambeau and Westwood, the top two finishers at last week’s Arnold Palmer Invitational, trailing but not totally out of the picture, Thomas came to the par-5 16th hole needing a daring strike. For his second shot from the fairway, Thomas hit a gutsy 5-wood that curled onto the 16th green from 228 yards. It was Thomas’s first attempt at an eagle putt in his career on the golf course’s 16th hole, which he did not make from 46 feet. But he tapped the ball in for a crucial, timely birdie.
“I was proud that I took some chances that paid off,” Thomas said.
A second successive second-place finish did not leave Westwood, who will turn 48 in April, dejected. He appeared at a news conference with a wide smile.
“I’m just having so much fun — everybody keeps telling me how old I am,” Westwood said, laughing. “I’m still out here contending for tournaments and playing in final groups with great players.”
DeChambeau said he had never hit a shot in competition like his knuckling mis-hit off the tee on the fourth hole Sunday, but he was not overly dispirited either.
“I don’t know what happened on four — that’s the game and I’m OK with it,” DeChambeau said. “Still smiling after. It just seemed like something wasn’t going my way today for some reason. I could just feel it. It was weird.”
Thomas, despite the outcome, was not without at least one moment of fear that one of his shots might find a water hazard at an inopportune time. His drive off the 18th tee landed only a few feet from the large pond to the left of the fairway.
“I thought it was 50-50 whether it was going to be dry or in the water,” Thomas said of the shot, which ricocheted to the right, away from the hazard, on its first bounce.
He continued, “When you win tournaments, you get lucky breaks like that.”