A month after McIlroy went from four ahead to 10 behind with a closing 80 at The Masters, his fellow Irishman was three clear after birdies at the 16th and 17th.

But McDowell then saw his approach to the last kick off the bank of a bunker and roll all across the green into the lake.

He double-bogeyed for "only" a third round 68 and 12-under-par total with 18 holes to play later in the day.

American David Toms and Korean KJ Choi were 11-under, then came a two-stroke gap to a six-strong group which included England's Luke Donald after he went in the water on the short 17th and bogeyed the last as well.

"I think I was a bit unlucky at the last," said McDowell. "When it landed I thought 'perfect', but then it started going down the slope and I thought 'trouble'.

"I guess it's a tough break, but I played great and I just want to have a chance coming down the stretch. That would be a lot of fun."'

McDowell resumed on the sixth green joint leader with Nick Watney, but while he parred his way to the turn the American birdied the eighth and ninth to go two in front.

However, Watney had a shocking inward half. First he hooked into water and double-bogeyed the 14th, then he dropped another at the 15th and from a greenside bunker at the 16th he skinned it into the lake.

He finished with a 72, but there was a worse finish than his.

Last week's winner Lucas Glover went in the water at the 16th and 18th. He took seven on both - double bogey, triple bogey - and fell six adrift after a 74.

Donald commented: "The finish leaves a sour taste. I hit a bad shot on the 17th and the 18th was even worse - I kind of got what I deserved.

"But I am still there or thereabouts and anything can happen on this course."

Both he and McDowell were trying to become the third European to win in four years. Sergio Garcia triumphed in 2008 and then Henrik Stenson 12 months later.

Alongside Donald were Ryder Cup captain Davis Love, his fellow Americans Watney, Steve Stricker and Jason Dufner and also Australian Aaron Baddeley.