Rory McIlroy produced a storming 3-3-3-3 finish to beat American Hunter Mahan on the 18th hole in the second round of the WGC-Accenture Match Play Championship, but the Irish teenager will not be meeting Tiger Woods after the world number one was knocked out by Tim Clark.

McIlroy began slowly and slipped to back early against Mahan but turned it around on the back nine with some perfect shots when he needed them most.

Two down after 12, the 19-year-old levelled the match with a birdie on13 and a par on the 14th. Another birdie on the par four 17th put him in control approaching the last.

Both he and Mahan landed on the green in two but when McIlroy holed a 20 foot putt there was no way back for the American.

Next up for the Holywood golfer is Clark, who ended Woods's comeback from injury, winning 4 and 2 at the Ritz-Carlton Golf Club near Tucson, Arizona.

Woods had marked his return after an eight month lay-off with a 3 and 2 victory over Australia's Brendan Jones in the first round yesterday, and he took an early lead with a birdie at the second today before Clark brought the match back to all square with a magnificent 68-foot putt at the fifth.

There was an upset in the making when Woods bogeyed the par-five, 659-yard 11th to lose the hole and then saw Clark birdie the 12th and 13th to go three up.

Some Tiger magic came at the 14th when he won the hole by holing out from a bunker but at the 15th he drove out of bounds into the desert and lost the match at the 16th to a player who came into the tournament ranked 32nd in the world.

"Well, I lost," Woods said. "I played really well today but didn't make enough birdies.

"When you're playing match play you have to make birdies and I didn't do that today.

"Tim's a wonderful player, he's consistent and grinds it out and he made a bunch of birdies today."

Woods' defeat meant he was the fourth of the top seeds in each quarter of the draw to be knocked out. Padraig Harrington and Sergio Garcia fell yesterday while Vijay Singh was beaten at the 19th hole tonight by England's Luke Donald.

It was a day of upsets all round as Oliver Wilson claimed another big-name victim when he knocked out world number 11 Anthony Kim.

The Ryder Cup rivals from last year were involved in a see-saw match with England's Wilson looking to claim a second successive upset having beaten KJ Choi in the first round.

Wilson, who with Henrik Stenson came from four holes down to beat Phil Mickelson and Kim in foursomes at Valhalla last September, tasted victory over the young American hotshot again with a 2 and 1 win.

Wilson now meets American Justin Leonard in the last 16 after the former Open champion defeated compatriot Davis Love III one up.

"Two good wins," Wilson said. "He's a great player and, obviously, the Ryder Cup I think maybe helped me a little bit, knowing that I've already beat him before.

"So I went out there just trying to play well and managed to do that, but it was a very tough match."

There was further success for England when Paul Casey reached the third round with a 6 and 4 win over Australia's Mathew Goggin and Ross Fisher ended the run of Pat Perez, the American who knocked out Harrington in the first round.

Fisher was five up after 10 holes and finished in style, sinking an eagle putt to send Perez to a 6 and 5 defeat.

Lee Westwood, though, could not get past American Stewart Cink, last year's runner-up, in a marathon match that went to five extra holes before the Englishman missed an 11-foot putt to send his rival through to meet Mickelson.

Mickelson reached the last 16 after beating Zach Johnson one up, but not before another back-nine scare.

Mickelson needed 19 holes to get past Argentina's Angel Cabrera in yesterday's opening round, having let slip a four-hole lead over the back nine.

Against 2007 Masters champion Johnson, a first-round winner over Northern Ireland's Graeme McDowell, he saw a four-up lead cut to one between the 14th and 17th holes before hanging on to win.

Colombia's Camilo Villegas, in Woods' bracket of the draw, was once again showing some hot form as he took a four-up lead over Spain's Miguel Angel Jimenez in the first five holes and maintained that for a 5 and 4 victory.

Villegas now meets Geoff Ogilvy, who kept the Australian flag flying with a 19-hole win over Japan's Shingo Katayama.

Sweden's Peter Hanson scored a 2 and 1 victory over Stephen Ames of Canada and will face Casey, while Fisher will play Jim Furyk, who beat Martin Kaymer of Germany 4&2.

Ernie Els of South Africa overcame American Steve Stricker 3 and 2 and now plays Donald.