Windy conditions quickly helped send scores soaring on the first day of the 118th US Open at Shinnecock Hills, with former champion Rory McIlroy one of the high-profile victims.

McIlroy and playing partners Phil Mickelson and Jordan Spieth were among the early starters hoping to take advantage of a course softened by Wednesday's rain.

But the four-time major winner McIlroy struggled to the turn in 42 as the marquee group combined to play the back nine in 15 over par with just two birdies between them.

It was also a day to forget for 2010 champion Graeme McDowell as he finished nine over following a 79.  

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The Hollywood native had been bullish about his prospects after a lengthy spell of preparation at Shinnecock and other courses on Long Island, but his prospects of a second US Open title were quickly blown off course.

After missing from seven feet for birdie on the 10th, his opening hole, McIlroy dropped shots on the next two holes and then ran up back-to-back double bogeys on the 13th and 14th.

McIlroy briefly stopped the rot with a birdie on the 15th, only to drop further shots on the 16th and 18th and then run up a double bogey on the first after a wayward tee shot.

He would finish at ten over following a round of 80. 

Mickelson finished at seven over (77), with Spieth a shot worse off after his 78. 

A resurgent Ian Poulter claimed a share of the clubhouse lead.

Poulter, who was ranked outside the world's top 200 just 15 months ago, carded a one-under-par 69 to join world number one Dustin Johnson and fellow Americans Scott Piercy and Russell Henley at the top of the leaderboard at Shinnecock Hills.

Justin Rose and Henrik Stenson are part of a large tie for sixth place on one over.

Jason Day shot 79 and former British Amateur champion Scott Gregory slumped to an unfortunate 92, the first score in the 90s in this event since 2002.

Tiger Woods fared only slightly better than McIlroy with a 78, which included a triple bogey on the first and consecutive double bogeys on the back nine, the first as a result of four-putting from long range.

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