Rory McIlroy and Lee Westwood are still on course for a semi-final clash at the Accenture Match Play Championship in Tucson.
McIlroy overcame Ryder Cup teammate Miguel Angel Jimenez 2&1 in Friday's third round, while Westwood beat Tiger Woods' conqueror Nick Watney - the man who had knocked him out the last two years - by a 3&2 margin.
It was the first time in 12 attempts that the Worksop golfer had made it into the last 16, but he looks in the mood to go much further. He next plays Martin Laird, who defeated fellow Scot Paul Lawrie 3&1 in a game which could have big implications for the Ryder Cup qualifying race.
Victory on Sunday would put Westwood back as world number one ahead of Luke Donald - McIlroy has the same target for the weekend - and so far he has repeated Donald's feat in winning 12 months ago, never trailing in any game and never being taken to the final hole either.
He has actually led for 48 of his 49 holes so far and said: "I feel in control of nearly every part of my game. I did some good work on my chipping last week and played some really nice ones. It was nice to get my own back. I didn't want to make it (losing to Watney) a habit."
He birdied the first two holes, went three-up after the American missed the green at the ninth, then stretched the gap to four by almost holing his approach to the next.
Westwood was bunkered on the 12th and lost it to a par three, but he did wonderfully well to halve the 583-yard 13th in birdies after his chip hit the hole and rolled 10 feet away. Halves at the next three finished things off.
Former Open champion Lawrie had gone all 18 holes before beating Justin Rose and Ryo Ishikawa, but was in trouble from the moment he bogeyed the first and Laird birdied the long second.
Laird stretched his advantage to three "against the head" at the short 12th, holing from seven feet and seeing the Aberdeen 43-year-old miss from five, but Lawrie's two-putt birdie on the next brought him back to two down. It was all over, though, when Lawrie failed to get up and down from sand on the 17th.
McIlroy turned three-up after some dazzling iron play. But for missing twice from under five feet and once from eight feet the 22-year-old third seed would have been out of sight. The gap twice came back to two early on the back nine, McIlroy twice fluffing chips, but he delivered the final nail in the coffin with another superb approach to the 17th.