Justin Rose shines with Justin Timberlake as Jordan Spieth and Jason Day struggle at Pebble Beach

Justin Rose made an encouraging start to the AT&T Pebble Beach National Pro-Am but Jordan Spieth and Jason Day both struggled on the opening day.

Rose fired a six-under 66 at Spyglass Hill, traditionally the tougher of the three courses in play this week, although he would have been disappointed at failing to build on a superb first 11 holes.

The Englishman made back-to-back birdies at the third and fourth as well as seven and eight to turn in 32, and he then holed his greenside bunker escape for another gain at the 10th.

The world No 7 got to six under with a deft up-and-down from the rough at the long 11th, but a poor tee-shot to the short 12th cost him his only bogey of the round.

After a steady run of pars, Rose closed with his seventh birdie of the day at the last to get within two strokes of early pace-setter Chez Reavie, who enjoyed an astonishing back-nine at Monterey Peninsula.

Rose, who partnered Justin Timberlake, said: "I've never seen a demographic like that on a golf course where you're sort of running the gauntlet from one tee to the other. Everyone was under 21 and 80 percent female.

"I said, 'OK, that moved the needle a little bit there.'"

Reavie was just one-under at the turn when his putter caught fire, converting birdie chances at five of the next six holes before rolling in another superb putt for an eagle at the 16th as he came home in just 30 blows to return a 63.

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The American held a one-shot lead in the clubhouse over Freddie Jacobson, who enjoyed a run of five birdies in six holes at Pebble Beach as the colourful Swede opened with a flawless seven-under 65.

Bronson Burgoon matched Reavie's back-nine 30 at Monterey Peninsula after starting on the 10th, but he had to settle for nine consecutive pars as he earned a share of second with Jacobson.

Four-time champion Phil Mickelson also got off to a solid start with a 68 at Spyglass Hill despite a bogey at his penultimate hole - the eighth - taking some of the gloss off his round, but the world's top two players both carded erratic 71s at the same course.

Spieth offset four birdies with three bogeys, while Day was one over after 12 holes before getting under the card for the day with birdies at the fourth and seventh.

Rose said the highlight was on the 16th tee when Timberlake grabbed a guitar for an impromptu performance, with Alfonso Ribeiro chipping in.

"That was a cool moment," Rose added. "Not many people saw it, because there was only like 20 people back there. 

"That's obviously when you really appreciate how someone can grab a guitar and sound so awesome. You have a better appreciation. You see him hit not maybe so many great golf shots, but then you realize, 'Ah, that's pretty damn special right there.' So we all have our own skill set."