Luke Donald and Louis Oosthuizen, the top seeds remaining after the shock first-round exits of Rory McIlroy and Tiger Woods, were bundled out of 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 said his game was "just very average".
Donald 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.
Ireland's Shane Lowry showed no let-down after his triumph over McIlroy, advancing with a convincing 6 and 5 victory over Sweden's Carl Petterson.
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.
That should get the semi-finals and the championship and consolation matches off as scheduled on Sunday.