Luke Donald and Louis Oosthuizen, the top seeds remaining after the first-round exits of Rory McIlroy and Tiger Woods, lost in the second round of the WGC Match Play Championship on Friday.
American Scott Piercy thumped England's world number three Donald 7 and 6, taking the lead at the first hole where Donald opened with a double bogey.
Piercy won the next two holes with a birdie followed by another bogey from Donald, and went 4-up at the fifth when he holed out from more than 200 yards away for an eagle.
He sealed the match with one last birdie, sinking a four-footer to close it out at 12. His victory over the 2011 winner of this World Golf Championships event was the most lopsided result of the week so far.
"I played well, and he was off a little bit," Piercy said. "That's why it looked so one-sided."
Donald, who characterized his game as "just very average," was the top seed in his quarter and third seed overall in the 64-man field behind world number one McIlroy and number two Woods, who both fell in the snow-delayed first round on Thursday.
Fourth overall seed Oosthuizen, a former Masters champion from South Africa, joined the exodus of bracket leaders as he was beaten 3 and 2 by American Robert Garrigus.
England's Justin Rose, the overall fifth seed, was also on his way home, falling 4 and 2 to Belgian Nicolas Colsaerts.
Ireland's Shane Lowry showed no letdown after his triumph over McIlroy, advancing with a convincing 6 and 5 victory over Sweden's Carl Petterson.
He's the first 64th seed to reach the third round in the 15-year history of the event. He booked a third-round match against another old friend from Northern Ireland, Graeme McDowell -- who finally put away Sweden's Alexander Noren at the 20th hole.
After a desert snowstorm cut short play on Wednesday, Friday's second round was a day behind schedule.
Organizers planned to get back on track with third-round matches on Saturday morning followed by quarter-finals in the afternoon.
Masters champion Bubba Watson advanced, finally subduing fellow American Jim Furyk at the 22nd hole.
Watson had built a 3-up lead through 10 holes, but Furyk rallied to square the match.
"It was a good match," Watson said. "I was up early. He made some putts, he missed some putts... I hit quality iron shots it seems like all day, but I just didn't make the putts, but somehow hung on to win."
US Open champion Webb Simpson moved on with a 1-up win over Sweden's Peter Hanson.
Simpson next faces Spain's Gonzalo Fernandez-Castano, who cruised to a 6 and 5 victory over American Charles Howell a day after Howell outdueled Woods.
Defending champion Hunter Mahan defeated South African Richard Sterne 4 and 3 and former champion Ian Poulter of England downed American Bo Van Pelt 3 and 1.