Rory McIlroy was left hoping that a careless three-putt bogey was not the difference between making the halfway cut and packing his bags at the US Open in San Francisco today.

The defending champion's shoulders sank when he missed a 15-foot birdie chance on the final green of his second round - and then he missed the tiddler coming back.

The bogey four meant a three over par 73 to add to his opening 77 and at 10 over he was resigned to making his fourth early exit from his last five tournaments.

"If the cut is nine (over) I won't be feeling too good tonight," said the 23-year-old Northern Irishman after clearing his locker and preparing to fly home.

World number one Luke Donald was on his way out too, a 72 leaving him 11 over and still waiting for his first major title.

There was disappointment of a different sort for McIlroy's compatriot and predecessor as champion Graeme McDowell.

Birdies at the 15th and 16th - his seventh and eighth holes of the day - lifted McDowell into second place on his own at two under par.

However, McDowell then bogeyed three of his last four holes and with a 72 slipped back to one over and joint ninth.

He was still right in contention, however, as most of those ahead of him were only just teeing off.