Luke Donald's defence of the WGC-Accenture Match Play title lasted only 14 holes in Arizona on Wednesday as he fell to a resounding 5&4 defeat against a resurgent Ernie Els.
England's world number one, who made no fewer than five bogeys, became only the third top seed to lose in the first round as he was hammered by this week's number 64 seed - Els was not even in the event until Phil Mickelson decided to go on holiday rather than make the trip to Tuscon.
Donald joins Tiger Woods and Steve Stricker in making an instant exit as top seed, they lost to Peter O'Malley and Ross McGowan respectively in 2002 and 2010.
Elsewhere, Robert Rock sprung another big surprise as he beat Adam Scott to advance to the second round, while an erratic Woods battled his way past Gonzalo Fernandez-Castano.
Neither Rock nor Scott was more than one hole up over the course of a scrappy match, but the contest turned at the driveable par-four 15th when the Australian gifted his opponent the hole with a wild tee-shot into the desert.
Rock then edged ahead after producing a birdie at the short 16th and held his nerve over the closing two holes to secure a notable scalp with a 1up victory.
Woods lost the opening two holes of his encounter as his Spanish opponent raced out of the blocks with two birdies, but would produce birdies of his own at seven and eight to lead at the turn.
However, the 14-time major champion followed a double-bogey at ten with a bogey at 11 to fall behind again and was fortunate that Fernandez-Castano did not take advantage of further opportunities to stretch his lead.
A bogey from the Spaniard at 16 saw Woods creep back ahead and the American then produced a brilliant up-and-down from a bunker at the last to close out a 1up triumph and secure a second-round showdown with compatriot Nick Watney who thrashed Open champion Darren Clarke 5&4.
A relieved Woods said afterwards: "Neither one of us had our best stuff - I was just surviving."
Rory McIlroy's dual with George Coetzee was the very last match of the day to finish, the Northern Irishman made hard work of closing out victory and was ultimately grateful to see the South African miss a short putt on the final green to confirm a 2up success.
Early exit for McDowell
YE Yang was the first man to book his place in the second round as he beat Graeme McDowell 2&1, thus overcoming the Ulsterman for the second year running at the event having also defeated the 2010 US Open champion in the third round 12 months ago.
After a see-saw start, the Korean moved ahead at the seventh and - despite a battling performance from McDowell - never trailed again, closing out victory on the 17th green after holing from three feet for birdie.
The second man through to the last 32 was 20-year-old Japanese player Ryo Ishikawa who knocked out FedEx Cup champion Bill Haas - winner of the Northern Trust Open in Los Angeles on Sunday.
Haas bogeyed the last to lose after standing three-up with five to go meaning Ishikawa will now take on Paul Lawrie, whose revival in the last two years continued with a last-green victory over Justin Rose.
Rose's close friend Ian Poulter also crashed out, the Englishman falling at the first hurdle for the second year running as he was soundly beaten 4&3 by Korea's Bae Sang-moon.
But there was better news for another Englishman as Lee Westwood put in a solid display to beat Belgium's in-form Nicolas Colsaerts 3&1, the world number three will next face Robert Karlsson who was a runaway 5&4 winner over fellow Swede Fredrik Jacobson.
Last year's beaten finalist, Martin Kaymer, comfortably saw off Australian Greg Chalmers 4&2 and will face an assignment against David Toms who got the better of a thrilling all-American affair with Rickie Fowler to emerge triumphant at the last.
Martin Laird was another to win on the final green as he outgunned Alvaro Quiros in a battle of the big-hitters, while experience won the day in the Spanish clash between Miguel Angel Jimenez and Sergio Garcia as the cigar-smoking veteran won out 2&1.
Laird now faces the youngest man in the field, Matteo Manassero, after the Italian's hugely impressive success over Webb Simpson, while Jimenez will take on Jason Day who came from three down with three to play to edge out another Spaniard, Rafael Cabrera-Bello, at the first extra hole.
Thomas Bjorn, conqueror of Tiger Woods at the 19th last year, went 20 holes on his return to the tournament - and then lost when Italian Francesco Molinari chipped in for an eagle.
American Ryder Cup team-mates Dustin Johnson and Jim Furyk went two extra holes as well, Johnson - who had been three down earlier on - had to take a penalty drop from a bush there, but scrambled a par and won when his opponent three-putted.