Rory McIlroy says he is 'relieved' that the US Open is over after a closing three-over-par 73 at Pinehurst left him tied for 23rd place on six over.
"I played a little better on Sunday but it's been a struggle. The course played progressively harder as the week went on," lamented the 2011 champion.
"I wasn't able to control my ball well enough to give me enough birdie chances and ultimately it frustrates you."
Graeme McDowell carded a 70 to end in joint 28th position on seven over.
The Portrush man posted three birdies and three bogeys in his final 18 holes but rounds of 74 and 75 on Friday and Saturday put pay to his chances after a promising opening 68 on Thursday.
"It was nice to finish with a better score but Friday and Saturday blew me out of the tournament," said the 2010 champion.
"This golf course is just very difficult - I didn't drive well enough and didn't get my iron shots close enough to the flag.
"When you are missing greens it grinds you down and my putter was not as sharp as it needed to be because I was putting with a lot of pressure on it.
"Overall, my game is not in bad shape - it's the start of a busy summer but I'm taking some good vibes with me."
McDowell admitted his frustration reached boiling point when he recorded four consecutive bogeys from the sixth to the ninth on Saturday, but the thought of picking up vital Ryder Cup points kept him going.
"What motivated me on the back nine on Saturday was that every dollar, every point, will count this summer. I was able to dig deep and I just have a few tweaks to make - I've a bit of work to do on driving the ball."
McIlroy registered two birdies but three bogeys and a double bogey six at the 12th blotted his card.
German Martin Kaymer secured his second major success, enjoying a comfortable eight-shot winning margin over Erik Compton and Rickie Fowler.