The American, who has made it to 37th in the world with hardly anybody noticing, sank his approach to the fifth for an eagle two and turned in a marvellous six under par 30.

Ian Poulter, who lifted the trophy three years ago, was almost as impressive as he made it through to the last 16 with a 3&1 victory over another of the home contingent in Bo Van Pelt, but fifth seed Justin Rose was another to bow out.

He was beaten 3&2 by Ryder Cup team-mate Nicolas Colsaerts.

Irish duo Graeme McDowell and Shane Lowry remained on course for a third round clash, meanwhile.

Lowry followed up his notable scalping of world number one McIlroy by moving four up on Carl Pettersson by the turn, while McDowell, having knocked out Padraig Harrington, was just ahead of another Swede, Alex Noren, as they started for home.

Donald, who returned from a long winter break only last week, had beaten German Marcel Siem with two closing birdies, but gave Piercy just the encouragement he perhaps needed by setting off again with a double bogey six.

The English star could never have expected to be six down by the so-called halfway point, though, and yet another birdie by Piercy on the short 12th finished things off.

Poulter, unbeaten hero of Europe’s triumph in Chicago last September and with match play crowns to his name on both sides of the Atlantic, has shown no ill-effects of taking six weeks off coming into the tournament.

“It feels pretty good,” he said.

“It was always a little risky taking that amount of time off, but it’s working out pretty well.

“I worked hard at home, put some new irons in the bag and I couldn’t be any fresher or fitter than I am right now.

“I didn’t make any silly mistakes and I guess making seven birdies you are going to be tough to beat.”

Having also eliminated Scot Stephen Gallacher, he next faces South African Tim Clark, who has so far defeated Adam Scott and Thorbjorn Olesen without having to play the final hole.

A Colsaerts victory was not that big a surprise in truth. The Belgian won the Volvo World Match Play in Spain last year, had eight birdies and an eagle in his first-ever Ryder Cup game and began this week with a crushing 5&4 win over American Bill Haas.

Rose actually won the first hole, but he could not match his big-hitting opponent’s birdie on the long second and by the seventh was already three down.

A birdie at the ninth and eagle on the 11th – both with 14-foot putts – hinted at a comeback, but the Englishman plugged his ball in a bunker on the next and Colsaerts hit his approach to two feet at the 14th.

The 15th was halved in birdie threes – Colsaerts drove the green on the par four – and it ended on the following green when Rose three-putted.

It is American Ryder Cup player Matt Kuchar next for Colsaerts.