Dustin Johnson runs away with Genesis Open and takes over No. 1 in world golf rankings

For three days, the Genesis Open was shrouded with unknowns, be it the weather, how Arnold Palmer’s grandson would do after leading, or if the golf tour would have a new world No. 1 after almost a year.

When the final round started around noon on a marathon Sunday at Riviera Country Club, there were absolutely no questions left to answer. Dustin Johnson had made sure of that, with a performance that was utterly dominating.

Johnson led by as many nine strokes early in the fourth round. He played the final holes as if he had a large lead and was content to protect it, explaining his final margin of five strokes. He finished at 17 under par.

When Johnson bogeyed the ninth hole, it was the first time he didn’t get a par or birdie in 50 holes. He followed with bogeys on 15 and 16 to shoot an even-par 71.

Johnson really won the tournament with a 64 in Sunday morning’s third round. He started the final 18 with a five-stroke lead and increased it with birdies on the first two holes and another on the sixth as others fell back.

“Today was a long day,” Johnson said. “Sometimes 36-hole days are good, especially because this morning I came out and played really well.

“To finally get a win in [Los Angeles] really feels good. I finished second here a couple times, lost a playoff. Felt like I should have won a couple other times. It’s certainly nice to win on a golf course I really enjoy playing.”

Thomas Pieters, whose final-round 63 equaled the tournament’s low round, must have felt like a dog chasing a Ferrari, with no chance to ever catch it. He finished at 12 under.

“I knew I couldn’t go 14 under on nine holes,” Pieters joked.

Also at 12 under was Scott Brown, who closed with a 67.

“I’ve never played good here over the last few years, so it feels good to get a good tournament in here,” Brown said.

Justin Rose, Wesley Bryan, Kevin Na and Charley Hoffman all finished at 11 under.

Johnson’s victory-clinching third round was achieved without requiring any exceptionally long putts. He birdied No. 1 with a putt from three feet, No. 5 (from five feet), No. 8 (13 feet), 12 (10 feet), 16 (nine feet), 17 (10 feet) and 18 (eight feet).

Johnson also ended Jason Day’s 47-week stay atop the world golf ranking. Entering the tournament, Johnson had a chance to catch Day if he won and Day finished worse than a tie for third. Day finished 64th at two over.

“Winning the golf tournament is most important right now,” Johnson said. “I came in here to put myself in a position to win, and I did that and played really well. I wasn’t really thinking about the world ranking. … I don’t really understand [the ranking] but I can read the 1-2-3.”

Day seemed resigned to giving up the No. 1 spot he’s held for almost a year.

“He deserves it because he’s been playing great golf,” Day said. “He goes ahead and wins this pretty convincingly. He deserves to get that ranking.”

It should have come as no surprise that Johnson would play well at Riviera, as he was well aware. Before this year he’d played the tournament nine times with five top-10 finishes. In 2015 he lost on the third hole of a three-man playoff won by James Hahn. He tied for third in 2010, was second in 2014 and fourth last year.

Johnson turned pro in 2007 and this was his 13th PGA Tour win. He won the U.S. Open last year at Oakmont, Pa., for his first major title.

After the long day, a major celebration didn’t seem in order.

“I got up at 4:30 [a.m.], right now the thing I’m looking forward to is getting in bed,” Johnson said.

Johnson is not the most famous athlete in his extended family. In 2013, he was engaged to Paulina Gretzky, daughter of hockey legend Wayne Gretzky. The couple have a boy, Tatum, and another child on the way.

Dustin Johnson shares the Genesis Open trophy with his son, Tatum.

(Christina House / For the Times)

The tournament was beset by weather delays from the start. It began Thursday with a fog delay, then play was suspended slightly after noon on Friday when a major storm moved into the area. By the time Saturday rolled around, some players, such as first-round leader Sam Saunders, hadn’t even started playing their second round.

Still, with a late finish Saturday and an early start Sunday, the tournament finished 38 minutes before sunset.

But for all intents and purposes, it ended five hours before that.

john.cherwa@latimes.com

Twitter: @jcherwa

UPDATES:

6:30 p.m.: This article was updated with quotes.

5:10 p.m.: This article was updated throughout with action from the final round.

2:30 p.m.: This article was updated throughout with action from the final round.

12:01 p.m.: This article was updated with the end of the third round.

10:45 a.m.: This article was updated with Dustin Johnson’s round through 13 holes as well as other golfers’ scores and progress.

10:16 a.m.: This article was updated with Dustin Johnson extending his lead to three strokes as well as other golfers’ progress.

This article was originally published at 8:40 a.m.