Luke Donald's defence of the Accenture Match Play title lasted only 14 holes in Tucson.
England's world number one became only the third top seed to lose in the first round when he was hammered 5&4 by Ernie Els - not even in the event until Phil Mickelson decided to go on holiday.
In winning last year Donald was never behind in six games and never taken to the final green either, but on his return to Dove Mountain the 34-year-old - who like Els finished the Northern Trust Open in Los Angeles on Sunday with a seven-over-par 78 - trailed from the third hole. Els finished things off with a 10-foot birdie putt on the 14th.
Ian Poulter, winner two years ago, was another of the first-day losers, suffering a 4&3 defeat to little-known Korean Bae Sang-moon, but three-time champion Tiger Woods came from behind for a one-hole victory over Spain's Gonzalo Fernandez-Castano.
In a scrappy match the Madrid golfer won the first two holes. Woods hit back to lead by one after eight, then hit wild shots and lost the 10th and 11th, but took the 15th and 16th and just held on. Bunkered in two on the last with Fernandez-Castano only nine feet away, he splashed out superbly down the slope to eight feet and was the one to make his putt.
Robert Rock, conqueror of Woods and the world's top four in Abu Dhabi last month, grabbed another notable scalp when he defeated world number eight Adam Scott. That came on the last, as did the victories by Scots Paul Lawrie and Martin Laird over Justin Rose and Alvaro Quiros respectively in two of six all-European clashes.
Lawrie, winner of the Qatar Masters three weeks ago, is making his first appearance in the tournament since 2003 and said: "It's great, but there is no point in playing these events if you are not going to play very well."
Second seed Rory McIlroy, left as Ireland's only hope after Graeme McDowell and Open champion Darren Clarke lost, was relieved to win on the last against South African George Coetzee after bogeying the 16th and 17th.
McDowell lost to Korean YE Yang for the second year running and said: "I made six birdies and played decent golf, but I ran into a man who played extremely well."
Clarke was crushed 5&4 by American Nick Watney, who next faces Woods, but Lee Westwood - never beyond the second round in 11 previous trips - overcame Belgian Nicolas Colsaerts. He and Rock are the only English survivors, Simon Dyson bowing out like Donald, Poulter and Rose.