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 yesterday.

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

The bogey 4 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 No.1 Luke Donald was on his way out, too, a 72 leaving him 11 over and still waiting for his first major title. Donald knew he needed something special after starting with a 79 and after the promise of an opening birdie – he did not have any on the first day – his chances slowly ebbed away.

"It was a little better today, but little consolation, obviously," he said. "I think I missed nine putts inside 10 feet yesterday and just couldn't get a feel for the greens. It wasn't to be, and I'm trying to learn from it and come back stronger next time. I feel I was prepared – I don't regret anything that I did before teeing up."

Last year, he admitted to overdoing things. "I think it was more a case of just not quite feeling too comfortable with the swing this week and that happens."

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

Birdies at the 15th and 16th lifted McDowell into second place on his own at two under. However, he bogeyed three of his last four holes and, with a 72, slipped back to one over and joint ninth.

"It's just tough to have fun out there, I've got to be honest with you," admitted McDowell. "It's just a brutal test of golf. I'm disappointed to bogey three of the last four, but that's what this golf course can do to you in a heartbeat, but I'm very happy to be where I am. I made enough birdies to kind of offset some mistakes, which I think is key."

He was still in contention, however, as most of those ahead of him were only just teeing off. They included American Michael Thompson, three clear overnight following a superb 66, but he bogeyed his third hole – the 430-yard 11th – to drop back to three under.

Tiger Woods was the favourite after his opening 69 and he remained one under and joint second with David Toms and Jim Furyk after surviving the 520-yard par-4 1st undamaged.

Lee Westwood was playing with McIlroy and Donald and he shot 72 to be five over, the same as Ian Poulter (75), while Justin Rose was one better after he, too, shot 75.