Shaun Micheel, the first round conqueror of Tiger Woods, continued his giant-killing run with a 4 & 2 win over Britain's Luke Donald in the World Match Play Championship quarter-finals.

The 37-year-old American now plays another member of next week's European Ryder Cup side, Robert Karlsson, after the Swede beat Argentina's Angel Cabrera 4 & 3 at Wentworth.

"When you beat the number one player in the world you are brimming with confidence," Micheel told reporters. "Someone's got to win this tournament and it might as well be me.

"It was a much better match today. Luke played really well all day, he just didn't make the birdies and that's what you've got to do in match play."

Holder Michael Campbell and Colin Montgomerie, the only former winners left in the field, were involved in an epic struggle which ended in a one-hole defeat for the New Zealander when he took two to get out of a greenside bunker at the 36th hole.

Montgomerie meets Paul Casey on Saturday after his Ryder Cup colleague recorded a 5 & 3 triumph over 2003 US Masters champion Mike Weir, who was barely able to swing the club after injuring his back on the 32nd tee.

Micheel carried on where he left off in his surprise 4 & 3 victory over Woods, producing the best golf of the day to go five up at lunch on world number 10 Donald.

The 2003 US PGA champion fired eight birdies in a seven-under-par 65, peppering the flagsticks with a succession of pinpoint approach shots.

Donald, who lives at nearby High Wycombe, went seven down when his opponent birdied the second and fourth holes.

World number 77 Micheel, whose PGA title is his only win on the US Tour, gave Donald hope when wayward approach shots cost him bogeys at the 11th, 14th and 15th before he finally ended the contest with another birdie at the 16th.

In the day's opening match, Campbell raced four up through six holes thanks to two birdies and an eagle at the fourth where he rolled in a massive 40-foot putt.

Montgomerie then showed the fighting spirit Europe will be relying on heavily in Ireland next week by clawing his way back to all square with three birdies in the last five holes before lunch.

The turning point for the 1999 champion came early in the afternoon round.

The 43-year-old Scot was forced to concede the fourth after driving out of bounds but showed the mistake had little effect on his positive frame of mind, calmly rolling in a 30-foot birdie putt at the next hole to go one up.

It was a lead Montgomerie never relinquished.

"I was four down before nine o'clock this morning, that's a helluva place to be," said the eight-times European number one. "He is gaining confidence with every hole and he is swinging the club better.

"That was difficult. My legs are very tired and I've got to try and get home and have a massage or something because I was struggling."

The four semi-finalists are chasing the richest first prize in golf, of £1 million.