Top-ranked defending champion Luke Donald was hammered by Ernie Els on Wednesday while Tiger Woods had a narrow first-round escape at the World Golf Championships Match Play Championship.
South Africa's Els dumped the Englishman 5-and-4, only the third time in event history the top seed has been ousted in the opening round. Els won five of seven holes from the eighth to close out the match on the 14th hole.
"I was trying to just take it as a first round match," Els said. "There's always hype when the No. 1 player is playing with the No. 64 seed but I think Luke and I took it for what it was.
"Obviously I can play a little bit of golf so I'm sure he didn't really want to face me. But that's the way it worked out. I played well. Luke had a bit of an off day and I'm obviously very pleased to go through."
Former World No. 1 Woods survived a scare before progressing through to the second day at the $8.5 million event.
Despite losing the opening two holes, Woods clawed his way back against unheralded Spanish World No. 46 Gonzalo Fernandez-Castano to win 1-up and set up a second-round match with fellow American Nick Watney.
Donald was left to lament one of his poorer days out on the golf course. His four bogeys left him hung out to dry.
The result also means he could lose his status as World No. 1 should No. 2 Rory McIlroy of Northern Ireland or No. 3 Lee Westwood of England go deep into the event. Both had reasonably comfortable first round victories.
"It's disappointing," Donald said.
"To lose control of the golf ball like I did today is really frustrating.
"I don't think it would have mattered who I played today. I gave away too many holes and made too many mistakes. You can't do that in match play against anyone, let alone Ernie."
McIlroy didn't hold back when asked about the chance to arrest the top spot in the world after his 2-up win over South African George Coetzee.
"To be honest, I came in here yesterday and talked about if I play well and just win matches that will take care of itself," he said.
"But obviously it's another incentive waking up each morning and knowing that if you win your match at the end of the week you could be World No. 1.
"We'll see what happens. I have to get through a lot of matches before that, but it definitely gives me an added incentive this week."
Facing a potential first-round elimination at the event for just the third time in his career, Woods won two of the last four holes and made a clutch up and down from a bunker on the 18th to seal the victory.
"I don't think either one of us had our best stuff today," Woods said. "We both made our share of mistakes. There's no doubt about that. But somehow I was able to move on."
Fernando-Castano was left to rue a great chance at victory.
"If there was one day to beat Tiger Woods, this was it," he lamented. "I didn't take the opportunity."
Top seeds in the other brackets moved on without much hassle.
Westwood had no trouble dismissing Belgium's Nicolas Colsaerts 3-and-1 and Germany's Martin Kaymer had an easier day out against Australian Greg Chalmers, triumphing 4-and-2.
Japanese superstar Ryo Ishikawa pulled off a miraculous comeback to upset last week's US PGA winner, Bill Haas.
Ishikawa, seeded 54th, was three down with five holes to play but won four of the final five holes, three with birdies, to take out the 11th seeded Haas 1-up.
"Through the first 13 holes, it had been really tough and I wasn't playing that well," Ishikawa said. "But the last five holes, I was able to compete."
If Ishikawa's comeback was miraculous, Australian Jason Day's was stupendous.
At three down against Spain's Raphael Cabrera Bello on the 16th green, World No. 7 Day thought he was gone with the Spaniard needing to make a six-footer for the match.
But Cabrera Bello blasted his putt well past and made back-to-back bogeys on 17 and 18 to allow Day a chance in extra holes. He gladly took the match on the 19th.
In other upsets, 57th seeded Englishman Robert Rock took down eighth seed Adam Scott 1-up, 53rd-seeded South Korean Y.E. Yang took care of Northern Ireland's 12th-seeded Graeme McDowell 2 and 1 and 19-year-old Matteo Manassero, the 59th seed from Italy, took down US sixth seed Webb Simpson 3 and 2.