DORAL, Fla. - Dustin Johnson might never escape the whispers about what led him to take a six-month leave of absence from golf that caused him to miss the final major of the year, the lucrative FedEx Cup playoffs and the Ryder Cup.

No one ever questioned his game.

He provided all the answers Sunday when he won the Cadillac Championship.

The power was evident on the monster tee shot he hit on the daunting 18th hole at Trump National Doral, so bold and pure that Johnson might have been the only one who never doubted it would clear the corner of the water and land safely in the fairway, setting up a routine par.

"I absolutely smashed it," he said.

The putting comes and goes, but it arrived when he needed it: The 20-foot par putt from the fringe on the 11th hole to stay one shot behind. The 10-foot par save on the 14th hole that gave him his first lead of the tournament. The 15-foot birdie on the next hole to seize control.

Also back was the swagger.

Johnson made up a five-shot deficit against J.B. Holmes, stayed in the game when Masters champion Bubba Watson looked as though he might run away, and powered his way to a 69-69 weekend and a one-shot victory for his second World Golf Championship title.

"I knew I was really good," Johnson said. "I knew there was something I was missing that could make me great. I was working hard on that, and I think it's showing right now. I'm so excited right now, I can't hardly talk. It feels great. This one definitely, by far, is the best one."

That much was clear when he walked off the green holding 7-week-old son Tatum and fiancee Paulina Gretzky, the daughter of hockey great Wayne Gretzky, at his side.

"Obviously, it's one of my biggest wins, and especially after a long layoff, to come back out and win in my fifth start, means a lot," Johnson said. "I've been working hard on my game and been working hard on me, and so it means a great deal to have some success right out of the gate. It gives me a lot of confidence, too."

He handled the inquiries into his personal life with just as much ease, even if he didn't have much to say.

Johnson announced in early August he was taking an indefinite leave to seek professional help for "personal challenges." Golf.com reported that day he had failed a second cocaine test — the first one was in 2012, the year he missed the Masters and was out for nearly three months for what he called a back injury from lifting a jet ski from the water. Johnson again said in his press conference Sunday evening that he has never failed a drug test.

When pressed why he had not been more forthcoming with answers, Johnson replied: "Because it's personal and, frankly, it's not really anybody's business."

Johnson lost in a playoff two weeks ago at Riviera. He tied for fourth, five shots behind, at Pebble Beach. He didn't look like a winner at Doral when the final round began, primarily because he was five shots behind and began the final round by missing a pair of 6-foot birdie putts.

He lingered long enough for everything to come together.

Holmes lost his lead after six holes, courtesy of three bogeys. He didn't make a birdie until the 16th hole, when he cut a 3-wood onto the green from 293 yards and two-putted for birdie. He couldn't convert two long putts for birdie down the stretch and closed with a 3-over 75.

"I thought 2 or 3 over would have been enough," Holmes said. "Just had a couple guys that needed to play well, and Dustin is it. He stepped up and played great. I was still trying to shoot under par. I wasn't trying to shoot 2 or 3 over."

He held his fingers a few inches apart to show the total length of putts he missed that he was sure would drop.

"You give me this much and I shoot 71," Holmes said.

Watson ran off four birdies in seven holes to start Sunday and had a two-shot lead. He went bunker-to-bunker on No. 11 for bogey. On the par-5 12th, he laid up in the rough and his third shot plugged into the face of the bunker, leading to another bogey. One more bogey followed from the palm trees left of the 14th fairway, and Watson didn't make a birdie coming in. He closed with a 71 and finished third, two shots behind.

"A couple of shots, just missed the fairway by a few feet. Missed the green by a few feet. That's what this golf course does," Watson said. "If you're just off, it can get to you real fast."

The final test for Johnson came on the 18th hole, where he had made bogey the previous three rounds. Water runs down the left side. Palm trees are to the right. There was no margin for error, especially with Holmes already in the fairway and one shot behind.

"Probably the best drive I hit all week," he said.

Johnson finished at 9-under 279, adding to the WGC title he won in Shanghai at the end of 2013. He was on top of his game, one of golf's most athletic figures who already had contended in three majors. Then came the indefinite leave.

And now, he's back.