By Mark Lamport-Stokes

MARANA, Arizona (Reuters) - Lee Westwood 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 Swede Peter Hanson advanced with a 5&3 win over American Brandt Snedeker.

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.

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-Scotland encounter.

In other matches, Northern Irish world number two Rory McIlroy was two up on Spaniard Miguel Angel Jimenez after 13 holes while South Korea's Bae Sang-moon was all square with Australian John Senden after 12.

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