He started with a three-putt six and was in the lake for another double bogey at the short 15th, but the most memorable moment came on the 207-yard 17th - scene of his triple bogey in the second round.

McIlroy, his right arm still bandaged after his incident with a tree root on Thursday, was perilously close to going into the water again.

But instead his ball hit the wall bordering the green, flew high up into the air and finished nine feet from the flag.

It left him wondering what would have come of the week if the same had happened 24 hours earlier, when he came to the hole only two strokes off third place.

“That would have been nice,” said the 22-year-old US open champion, who came into the week as clear favourite.

“Yeah, I think there were two pivotal moments in this tournament for me - obviously the shot on the third on Thursday (the one he admits in hindsight he should not have attempted) and the six-iron on 17 yesterday.”

Although he added that his pronator muscle was still “quite sore”, it was his putting that cost him dear.

“I couldn’t get my speed at all on the greens. I’ve struggled with it all week.

“I’ve got one more day to go. Hopefully give it my best and shoot a good score and take a couple of weeks off.”

He is next due in action at the European Masters in Switzerland on September 1-4 – it is the first event of the Ryder Cup race – and once home he thinks he might not hit a ball until he gets there.

“I’ll just make sure that it’s okay for a couple of weeks’ time. I want to try and finish as high up in The Race to Dubai as I can.

“Looks as if Luke has it sealed up – he’s got it going well again today - because I want to try to end the season well.

“Even though I won one tournament and it was a major, I still want to win a few more times to call this season a success.”

McIlroy did not fail to mention that his best round of the week – an opening 70 - came when his wrist hurt the most.

“Maybe I shouldn’t have gone and got it strapped up!” he added.

World number one Donald, who leads both the European and American money lists but wants a first major more than either of those accolades, was indeed going well.

After a bogey on the second he birdied the next three and with another on the ninth for an outward 32 was up to joint 10th place on two under.

That was three behind shock overnight leaders Jason Dufner and Keegan Bradley, who had yet to resume.

World number two Lee Westwood, one under at halfway, resumed with three pars, while stablemate Simon Dyson birdied the second and fourth to reach two under, but then double-bogeyed two holes later.

There were plenty of worse scores than McIlroy’s.

Paul Casey, in danger of missing the PGA Tour’s FedEx Cup play-off series like Tiger Woods, was in 75th and last place after a 78 that included an eight on the 467-yard eighth.

Padraig Harrington matched McIlroy’s front nine 40 and with one to play was alongside him on seven over.

Ian Poulter dropped five shots in the first four to slump to seven over before regaining some form, while Ross Fisher, level par after 36 holes, bogeyed the first, fifth and sixth.