Pacific Palisades - Rory McIlroy's first taste of Riviera Country Club went off without a hitch on Thursday while any competitive advantage Jordan Spieth was supposed to have quickly vanished in the opening round of the Northern Trust Open.
World number three McIlroy blasted his way to a four-under par 67 in his tournament debut while American Spieth, the reigning Masters and US Open champion, slumped to one of the worst rounds of his career on a course he has played more than 30 times in five previous visits.
Riviera is considered a shotmaker's course and while four-time major champion McIlroy had his game in high gear, Spieth did not as his eight-over 79 resulted in a 12-stroke swing between two of the sport's brightest young stars.
"It is just a day to forget and I won't think much on it," said Spieth, who shared fourth at Riviera last year.
World number one Spieth is 16 strokes back of clubhouse leader Camilo Villegas, who shot a sizzling 63.
The first round was halted because of darkness with 14 players still on the course. It will resume early Friday followed by the start of the second round.
Americans Chez Reavie, Bubba Watson and Luke List are tied for second after shooting five-under 66s.
McIlroy headlines a group of seven who finished their first rounds in a tie for fifth.
The 26-year-old Northern Irishman is switching up his pre-Masters schedule, which is why he decided to enter this week's $6.8 million US PGA Tour event.
Thursday was the first time in his seven seasons that he has played a round on the US west coast swing.
"It is always nice to come to a historic golf course," McIlroy said. "I just wanted to get a good start. I didn't want to put myself behind the eight ball early."
McIlroy finished with five birdies, one bogey and 12 pars on the 7,349 yard, par-71 layout.
One of his best holes of the day was the par-four seventh, where he stuck his approach shot from 143 yards to three feet, setting up a birdie.
McIlroy said overnight rains helped make the course easier to play.
"I put myself out of position sometimes but with the way the golf course was playing it didn't punish you much," he said.
"It happens a handful of times a year that we get to play a historic course like this. You got Augusta and we had it last year with Royal County Down in Ireland and you've got this course."
McIlroy dropped to number three in the world this week, losing ground to Australia's Jason Day.
Spieth and McIlroy have met just twice since Spieth won the Tour Championship in October. Spieth finished seventh and McIlroy 11th in China and McIlroy was third and Spieth fifth in Abu Dhabi.
Spieth had eight bogeys and one double bogey as he fired the worst first round of his career. He has shot in the 80s just twice - the third round of the 2013 Memorial and the third round of the 2014 Tour Championship.
Weather forecasters are predicting sunshine over the next few days, which Watson says should make for a competitive final round.
Seven of the past 15 tournaments at Pacific Palisades have gone to a sudden-death playoff - including three times in the past four years.
"It [course] could get all baked out and be a lot tougher," Watson said.
Leading first-round scores here on Thursday in USPGA Tour's Northern Trust Open (round halted because of darkness with 14 players still on the course, USA unless noted):
63 - Camilo Villegas (COL)
66 - Chez Reavie, Bubba Watson, Luke List
67 - Charlie Danielson, Charles Howell, Ricky Barnes Justin Leonard, Shawn Stefani, Ben Crane, Rory McIlroy (NIR)
68 - Martin Laird (SCO), Luke Donald (ENG), Harris English, Billy Horschel, Troy Merritt, Jason Kokrak, Dustin Johnson, Kyle Reifers, Kevin Chappell, Charl Schwartzel (RSA), Retief Goosen (RSA), Adam Scott (AUS), Marc Leishman (AUS), Angel Cabrera (ARG)
69 - KJ Choi (KOR), Hideki Matsuyama (JPN), Francesco Molinari (ITA), Jamie Lovemark, Chris Stroud, Ryan Moore, Will MacKenzie, JJ Henry, Justin Rose (ENG), Peter Malnati, Matt Kuchar, Jamie Donaldson (WAL)