Hunter Mahan, the man whose defeat to Graeme McDowell decided the last Ryder Cup, raced into the semi-finals of the World Golf Championships-Accenture Match Play Championship in Tucson.

After overcoming Celtic Manor teammates Zach Johnson and Steve Stricker in the first and third rounds Mahan sent another - World Number 14 Matt Kuchar - on his way home by a 6 and 5 margin.

Kuchar, third in the event last year, was a shadow of the player who had knocked out fourth seed Martin Kaymer the day before.

He three-putted twice and had four bogeys as he turned five down, then went over the green and dropped another stroke on the next.

Mahan added to his opponents misery by halving the long eighth in birdie fours and then rolling in an 18 footer for another birdie at the next.

Kuchar did birdie the 11th and 13th, both par fives, but so did Mahan and that was that.

It looked like being fellow American Mark Wilson next for Mahan. A winner on the US PGA Tour already this season, Wilson led Swede Peter Hanson by three with five to play.

Hanson fell behind for the first time all week when he bogeyed the first, but there was never more than one in it until the European Ryder Cup player went into the desert scrub for the second successive hole on the long 11th and ran up a bogey six.

He was then in two bunkers at the 13th and despite rescuing a par five it was not good enough to save him from losing another hole.

Rory McIlroy's clash with Korean Bae Sang-moon and Lee Westwood's match with Scot Martin Laird did not start until much later.

The second and third seeds each needed to win the title on Sunday to take the World Number One spot off Luke Donald, but after five holes McIlroy was on level terms, while Westwood trailed by one after four.

McIlroy made the perfect start with an eight foot birdie putt, but found the lake at the short third. Behind him Laird's six footer on the first meant Westwood trailed for the first time in the tournament and they shared the next three.

There was to be no comeback from Hanson. He had his third bogey in five holes at the 14th and was shaking hands on the next green when Wilson matched his birdie three to clinch a 4 and 3 victory.

McIlroy and Bae were still level after seven and Westwood got back on terms with Laird by getting up and down from sand at the short sixth, his opponent flying the green and then chipping off the other side.

Mahan admitted he was surprised at how poorly Kuchar played given "the level of game he has", while the short-hitting Wilson commented: "They talk about it being a bomber's course, but you have to hit it straight too."

That point was proved by the last two winners - Ian Poulter and Donald are by no means big-hitters - and Wilson had had only six bogeys in four games.

McIlroy nosed in front again with a six foot birdie putt on the 576 yard eighth, but he was under a bush off the tenth tee, took a penalty drop and bogeyed to be back at all square.

Westwood, meanwhile, was gifted the sixth, seventh and ninth, Laird missing all three greens and bogeying to go from one up to two down at the turn.

McIlroy went two-up with birdies at the 11th and 13th and Westwood held the same advantage with six to play. Laird's fourth bogey in five holes came after he drove into the desert at the tenth, but he took the next when he chipped to three feet and saw his opponent three-putt.