Donald, Oosthuizen out of Match Play
Donald and Oosthuizen follow world No 1 and 2 McIlroy, Woods out of Arizona championship
Luke Donald and Louis Oosthuizen followed Rory McIlroy and Tiger Woods out of the World Golf Championships Match Play Championship with second-round defeats.
One day after the fickle nature of the match-play format was amply demonstrated by the first-round upsets of world No 1 McIlroy and No 2 Woods, seeds continued to tumble.
American Scott Piercy thumped England's world No 3 Donald 7&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 characterised his game as "just very average", was the top seed in his quarter and third seed overall in the 64-man field behind McIlroy and 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&2 by American Robert Garrigus.
England's Justin Rose, the overall fifth seed, was also on his way home, falling 4&2 to Belgian Nicolas Colsaerts.
It marked the third time in the last five years that the top four seeds failed to make it past the second round.
By the end of the day, reigning Masters champion Bubba Watson was the only one of the tournament's top 10 seeds remaining - and only after battling to a victory over Jim Furyk at the 22nd hole.
"This game ... it's a toss-up," Watson said.
"You can't really judge who's going to win, or bet who's going to win. It really means nothing," he added.