Published Friday, 15 June 2012
Rory McIlroy of Northern Ireland reacts to a poor first round on the 18th green (© Getty)
The 23-year-old began his defence of the US Open title on Thursday with a seven-over-par 77.
It left him 11 strokes behind surprise leader 27-year-old American Michael Thompson, who has previously not placed in the top 100.
McIlroy still scored one better than Masters champion Bubba Watson and two less than world number one Luke Donald.
"It's just so tough here if you put yourself out of position at all," said McIlroy after initially not speaking to the press.
"Too many times I just was in the wrong position off the tee or with my second shot."
He said it was hard to catch up on the San Francisco course and that he would need to limit any mistakes on Friday.
"You have to be so precise. Anything just a little off and it really punishes you," he said.
"I tried to approach it like any other tournament I play and tried to go out there and shoot the best score I could."
It wasn't my greatest day, but hopefully I can come out tomorrow morning and try and shoot a good one and at least try to be here for the weekend.
McIlroy was playing with Donald and Lee Westwood, who after a double bogey on the first battled hard for a 73.
Donald admitted he had found it hard on the course and could not hide his disappointment after failing to make a single birdie in his 79.
"In the US Open the margins are that much smaller and if you're just a little bit off it's tough," he said.
"My putter kind of went cold, otherwise I could have probably ground out some more respectable score.
"The top three in the world and we make three birdies between us - it shows how tough it is.
"I tried to stay patient, tried to stay positive, but when I had those opportunities on the greens I couldn't take them."
He said the trio mostly concentrated on their own game
"There was a little bit of chat out there, but not too much. The US Open demands your full attention and obviously Lee had a good back nine (one under after all three turned in four over), but Rory and I both struggled," he said.
Thompson, runner-up in the US Amateur on the course five years ago and ranked 107th in the world, leads by three just as McIlroy did after the opening round in Washington, he covered the last 12 holes in six under for his 66.
Tiger Woods is now an even stronger favourite, his 69 was good enough for a share of second place with 2010 winner Graeme McDowell, England's Justin Rose and two more Americans, Nick Watney and David Toms.
Watney ensured his place on the leaderboard after sinking a 190-yard five-iron on the long 17th for only the third albatross in US Open history.
McDowell and Rose both finished with a brace of birdies late in the day to give the 36-strong European contingent a presence on the leaderboard.
With organisers changing the game, only the leading 60 and ties after the second round will continue into this weekend.