MIAMI • Golf's world No. 1 Jordan Spieth was left staring down the barrel of his second missed cut of the year on Thursday, after firing a five-over 76 in the opening round of the Valspar Championship.

The defending champion, who missed the cut at the Northern Trust Open in Los Angeles last month, suffered a torrid round on the Innisbrook Resort's challenging Copperhead layout to finish the day way off the pace.

The American, who struggled to get to grips with the blustery conditions, carded six bogeys and one birdie and will need to produce something miraculous this morning (Singapore time) if he is to extend his role into the weekend.

"It was a very tough day. I just didn't hit enough greens," said the 22-year-old, who never recovered after a disastrous start which included five bogeys and one birdie in his first seven holes to put him four over at the turn.

"I got off to a poor start and I was behind the eight-ball with gusty wind on a tough golf course."

Spieth was also dismayed with his putting performance on the slow greens. "It's so tough on some of these putts down the hill to hit them as hard as we have to hit them," he said. "It's one thing to practise on the greens and get used to it, it's another to actually do it."

He was left nine shots adrift of early pace-setters Keegan Bradley, Ken Duke and Charles Howell III, who all carded 67s to take a share of the first-round lead.

Bradley shot five birdies and one bogey, a haul which included a superb 25-foot birdie putt at the par-three fourth.

Unlike Spieth, Bradley was happy with the condition of the greens. "I think this is a great speed for these greens," he said.

The 29-year-old American, however, admitted that the wind had caused him problems. "It seems to be very up and down, it was a tough round," he said. "The course is so good because if you hit good shots, it really rewards you."

Journeyman Duke, who has not won a PGA Tour event since 2013, joined Bradley at the top of the leader board after conjuring up a final-hole chip-in from the edge of the 18th green for his fourth birdie of the day.

Howell was flawless, finishing with 14 pars and four birdies. The highlight was a monster 45-foot birdie on the par-five 11th.

The highest non-American players on the leader board included England's Danny Willett, Sweden's Jonas Blixt, South Africa's Retief Goosen, Germany's Martin Kaymer, New Zealand's Danny Lee and Australia's Cameron Smith, who all shot 70s.

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