Drysdale, 290 places below him on the rankings, could not believe his luck as his second shot to the final hole went into the water and bounced out again.

“You could hit 1,000 balls and never have that happen,” said the 37-year-old Scot, who went on to birdie the par five for a six-under 66 and a share of the lead with Ireland’s Peter Lawrie.

“I don’t know what it hit – maybe a fish. It was a massive break. I don’t think I can say what I would have thought if I had taken six or seven there.”

McIlroy’s show of frustration, which could result in a European Tour fine, came as he ran up a six on the long 12th.

It was the last of four bogeys in five holes and a double bogey at the 16th was to follow. He had earlier eagled the fourth.

Having started with a 76 last May, the Northern Irishman this time said: “A bit of deja vu. Two under through seven, so it’s just pretty disappointing.

“I feel like I’m playing pretty well. I just need to go out there and shoot the scores.”

On the shot at the 12th, McIlroy added: “I was just trying to cut it in, trying to hold it up against the wind and just double-crossed it.”

Tournament director David Garland said in a statement: “I have not yet had the chance to view the incident, but I will be requesting a tape.

“If any breach of the Tour’s guidelines on course etiquette is found, then appropriate action will be taken in due course.

“But any decision is unlikely to be taken until after the tournament has finished.”

McIlroy crashed out early from the Players Championship in Florida two weeks ago and might need a four-stroke improvement tomorrow to survive this time.

If the 23-year-old does fail to make it through to the weekend, Donald will need a top-eight finish to go back to number one, but he is aiming much higher than that after a 68.

With a chance to join Nick Faldo and Colin Montgomerie as the only players to make a successful defence of the European Tour’s flagship event, Donald bogeyed the ninth and 10th like McIlroy, but had already had four birdies and two more were to come in the last three holes.

That still made him the highest scorer in his group, though. Compatriot Justin Rose and big-hitting Spaniard Alvaro Quiros both scored 67, Rose after fearing he might have to pull out before the start because of vertigo-symptoms.

“An hour before my tee time I thought, ’I can’t play’,” Rose said. “I was nearly falling over and was sitting in the doctor’s chair for a while.

“He gave me an anti-nausea or something and did a good job getting me ready. I felt fine all the way round.”

McIlroy was the highest scorer in his three-ball. Ernie Els, the man who toughened up the course two years ago, shot 68 and US-based Scot Martin Laird, runner-up at Sawgrass, had a 73 on his debut in the championship.

Lee Westwood, whose play-off defeat to Donald 12 months ago cost him the number one position, returned a 70 and was delighted with that, saying: “I didn’t have anywhere near my A-game and not even my B-game really.”

The two pacesetters, Drysdale and Lawrie, are both outside the game’s top 200, with former Spanish Open champion Lawrie currently standing 212th.

Lawrie was also the joint leader on the first day in 2006 and did not waste a blistering start in which he eagled the fourth and birdied the second, fifth and sixth.

The Dubliner said: “I played so well in practice that I was kind of very nervous starting out.

“I missed a couple coming in, but 66 can’t be snoozed at. The course is set up great for me – I’m not one of the longest hitters on tour, but one of the straightest.

“You have to very patient and I’m quite a patient person. My wife wouldn’t believe that, but I am on the course!”