Lee Westwood, though, was back into a tie for the lead after finishing his second round with a double-bogey six.

McIlroy’s tournament had begun on Thursday with a double bogey and he had another on the 445-yard first today.

This time the US Open champion’s second shot went over the green, he then chipped off the other side and his next attempt ran back down the slope in front of the flag.

Back on the course where he went from four ahead to 10 behind with a closing 80 last April, McIlroy saved par from the guarding bunker at the short fourth, but by dropping another shot on the 455-yard next was back to one under par.

That put him four behind Westwood, who had birdied the long second, and Americans Jason Dufner and Matt Kuchar, who holed a bunker shot on four and then hit his approach to the seventh to within a few feet.

Dufner, who blew the USPGA Championship last August and does not have a single victory on the PGA Tour, also birdied the second, but bogeyed two holes later after going right of the green.

Playing partner Couples, the oldest man to set the pace in The Masters at halfway, bogeyed the first two holes and then double-bogeyed the fifth, while Garcia, who had been one behind overnight like McIlroy and Westwood, dropped shots on three of the first four.

Justin Rose made a big move from 24th to joint third by covering the first 14 holes in three under, but then was desperately unlucky on the 530-yard 15th.

He went for the green in two and just made it, but after appearing to come to rest the ball started rolling back and finished in the water. It cost him a bogey six, but he was right in the thick of the action a month after grabbing his first world championship title.

Luke Donald counted himself out, however, after a 75 for seven over – it could well cost him the world number one spot – and the 72 by Tiger Woods that kept him at three over was almost certainly the end of his chances.

After the thrill of pitching in for an eagle two on the third and thinking he could climb back into contention, Donald went in Rae’s Creek on the 13th and ran up his second seven of the week.

“There’s nothing worse than waking up on a Sunday and whatever you do is not going to be good enough,” the 34-year-old said as he dropped outside the top 50.

Even if Donald climbs around 10 places in the final round McIlroy would need only to finish only 20th to take back the number one spot, although that was no given any more

There was also the possibility of Westwood regaining the position he last held last May, before Donald beat him in a play-off for the BMW PGA Championship at Wentworth.

He needed to win his first major title to have a chance of leapfrogging over Donald and McIlroy.

Woods, completely off-form in his second round 75, birdied the third and fourth, but bogeyed the sixth and ninth and parred in.

Amazingly, he has managed only one birdie on the par fives all week – one out of 12 attempts, that is – and on the 13th did well to make his five after hooking his drive into the creek.

It was Donald’s second shot that found the water there.

“I thought I hit a decent shot,” Donald said of his three-iron, “but it missed carrying by two inches.”

After a penalty drop he skimmed his pitch over the green and three-putted – as he did on the 14th.

Missed putts of six feet on the 16th and 18th just piled on the agony.

“I had high hopes for this week,” he added. “I will think about my build-up, but I felt ready. At least I won some crystal for the eagle – that’s about the only high.”

Worse was to come for McIlroy and Rose. The former three-putted the seventh for yet another double bogey and was 30th amazingly, while Rose four-putted the 170-yard 16th for a double bogey five and slumped to 17th.

Dufner had trouble himself, three-putting the sixth to leave Westwood and Kuchar sharing top spot.

Henrik Stenson, who finished the first day with a quadruple-bogey eight that tied the tournament record on the hole, became the sixth player to have at least share of the third-round lead when he birdied the short 12th.

But it was short-lived. Even before the Swede bogeyed the next, Kuchar went to six under with a 12-footer on the ninth and 2010 Open champion Louis Oosthuizen joined him with a hat-trick of birdies from the sixth.

Three in a row was good, but Padraig Harrington had four successive birdies from the 13th and was up to three under.

Westwood, though, could not get up and down from sand at the seventh and was two behind after his first bogey of the day.

Phil Mickelson, meanwhile, birdied the 10th and 12th to be part of a six-way tie for fourth – and that after a triple-bogey seven on the 10th in his opening 74.

McIlroy bogeyed the long eighth and his front-nine 42 was only one better than his back-nine meltdown last year.

He had dropped 31 places to 34th, whereas Harrington’s closing 15-foot putt for a fifth birdie in six holes made him the early clubhouse leader on four under with playing partner Hunter Mahan. Both were round in 68.

Westwood was only 10th after a shocking three-putt bogey at nine. His birdie attempt had been from only 10 feet and his next effort, which horse-shoed out, from little more than a foot.

In contrast to that, however, Mickelson rammed home a curling 25-foot eagle putt on the 13th – and with it joined Kuchar and Oosthuizen in the lead.