Graeme McDowell pulled off another incredible comeback to beat Hunter Mahan at the 21st to reach the quarter-finals of the WGC-Accenture Match Play Championship.

Having risen from the “dead” to beat Gary Woodland at the 19th and Hideki Matsuyama at the last in the first two rounds, the Portrush battler recovered from two down with two to play to take his 2010 Ryder Cup victim into sudden death and beat him with a birdie at the third extra hole.

A crucial three-putt from 18 feet at the 16th left McDowell two down and facing what looked like certain defeat after an average day on the greens. But 34-year old won the 17th by holing a gusty 10 footer for par and then hit a sensational 181-yard eight iron to six feet in the last and rolled home the birdie putt to force sudden-death.

The first extra hole was halved in par fours but McDowell – who has now played 58 holes this week without ever standing on a tee box with the lead – had to hole a 20 footer for a half in par at the 20th (the ninth) to stay alive.

It all ended at the 21st when McDowell hit a huge drive and a perfect second to 14 feet and holed the birdie putt as Mahan buried his tee shot in the left rough, came up in the waste area short of the green but never got the chance to hit his putt.

McDowell now faces Victor Dubuisson of France in the quarter-finals which will see Louis Oosthuizen face Jason Day, Jim Furyk versus Rickie Fowler and Ernie Els against Jordan Spieth.

“Yesterday I thought I had a chance but today, two down with two to play against a quality player like Hunter Mahan, I thought I was done,” McDowell said.

“The par save at the second play off hole was just ridiculous. I can’t believe it really. I have just robbed three players at this tournament. I can’t believe I am still in it.”

He had gotten off to a horrific start for the third day running when he bogeyed the first, ramming his putt from the collar of rough behind the pin some eight feet past the hole before missing the return.

He then drove into sand at the second but despite recovering with a brilliant third to eight feet, he missed against to go two down.

Mahan handed him the par-three third by dumping his tee shot in the lake and taking five. But while McDowell then levelled the match with a tidy chip and putt par at the fifth, where Mahan was in trouble off the tee, he could never get his nose in front.

It looked as if he would finally stand a tee with a lead after he hit a six iron to just six inches at the par-three sixth. But Mahan followed him in from nine feet to remain all square.

McDowell then had chances to edge ahead at the eighth, ninth and 10th but a missed three putts of around 12 feet each time.

Mahan finally took the lead again by getting up and down from greenside sand for a winning birdie four at the 11th after McDowell had been forced to lay up after bunkering his drive.

A birdie four at the 13th was only good enough for a half but Mahan opened the door at the 14th, taking six to allow McDowell to square the match again. McDowell’s hopes faded when he lost the 15th, missing a nine footer for birdie before Mahan drilled home a four footer.

Looking back at last season, McDowell admits he was “fried” during the 2012 Ryder Cup at Medinah, where he won just one point out of four.

But by paring down his schedule and taking a longer winter break than normal, he hopes to be buzzing for the majors and the Ryder Cup at Gleneagles. “As I hit my mid 30s, I’m trying to try to get my calories expended better than my intake,” McDowell said.

“I enjoy a few glasses of red wine, I’m not going to lie. And I think being serious about it, I’m disappointed with my performance in August and September for the last few years.

“I look back to two years ago at Medinah, I was fried at Medinah, and I was fried at the FedEx playoffs. Last year I was fried at the FedEx playoffs, again. I don’t want that to happen this year.

“I’ve made a few decisions, I’ve cut back on a little golf course activity. I’ve tried to up my fitness regime and get leaner and fitter just to try to be ready for August and September this year, really. That’s the big goal of mine. Obviously I want to be on the Ryder Cup team and I want to be prepared when that comes around this year.”

The day was marked by an act of sportsmanship by Sergio Garcia, who was just four feet away when he conceded an 18 foot putt to Rickie Fowler for a half on the seventh to make up for taking an age to play the par-three sixth.

The Spaniard’s ball had ended up next to a sprinkler head that was surrounded by bees attracted to the water. He asked for and got a free drop but took so long over it that he said “good-good” in offering Fowler a half at the next.

Garcia was three up after eight but ended up losing one down as the American staged a back nine comeback.