By Mark Lamport-Stokes

MARANA, Arizona (Reuters) - Lee Westwood, oozing confidence, reached the last eight for the first time at the WGC-Accenture Match Play Championship while Germany's Martin Kaymer became the biggest casualty in Friday's third round.

World number three Westwood never trailed on his way to a 3&2 victory over American Nick Watney but Kaymer, beaten by Luke Donald in last year's final, was ousted 4&3 by American Matt Kuchar at Dove Mountain's Ritz-Carlton Golf Club.

Hunter Mahan completed another upset when he stunned U.S. Ryder Cup team mate and world number five Steve Stricker 4&3 after a sizzling display in the Sonoran desert and Northern Irish world number two Rory McIlroy beat Spaniard Miguel Angel Jimenez 3&1.

Kuchar became the first player to reach the quarter-finals, coming from one down after three holes with a rock-solid performance as Kaymer perpetually struggled on the tricky, heavily contoured greens at Dove Mountain.

"Matt played very consistently," Kaymer told reporters. "He didn't make any mistake really, but I made a few today unfortunately.

"I hit a lot of good quality golf shots today, especially the first nine. I didn't miss any golf shots really, but I just couldn't make the putts."


World number 14 Kuchar struck his tee shot to within two feet of the cup at the par-three sixth for a conceded birdie to go one up before his lead was doubled when Kaymer three-putted from six feet to bogey the par-five eighth.

The consistent American then birdied the 10th and 11th to go four up before sealing the win with a matching par on the 15th green.

Westwood, who would return to the top of the world rankings if he wins Sunday's final, was delighted to beat Watney, having lost to the American in the second round in 2010 and again last year.

"I knew it was going to be a tough match against Nick," the Englishman smiled. "It was nice to not make that hat-trick and to win, get through to tomorrow and see what happens on the weekend."

In-form Mahan piled up nine birdies in dazzling sunshine, the last of them conceded by Stricker from just two feet at the driveable par-four 15th to end their third-round encounter.

"I felt good with my game," said Mahan, who will face Kuchar in Saturday morning's quarter-finals. "Irons, driving, everything, putting, chipping ... I just had a lot of confidence in it.

American Mark Wilson reached the last eight for the first time with a 4&3 victory over big-hitting compatriot Dustin Johnson and Martin Laird beat 1999 British Open champion Paul Lawrie 3&1 in all-Scottish encounter.

In other matches, Swede Peter Hanson advanced with a 5&3 win over American Brandt Snedeker while South Korea's Bae Sang-moon won a tight tussle with Australian John Senden one up.

(Reporting by Mark Lamport-Stokes; Editing by Frank Pingue/Patrick Johnston)