Luke Donald was the biggest casualty on the first day of the Accenture World Match Play with the world number one going down to Ernie Els 5&4.
The top seed and defending champion went behind as early as the third hole and from there it was a struggle for the 34-year-old as Els produced some sublime golf.
The South African may have needed players to withdraw to make it into the draw but he looked sharp as he sank a 10-foot birdie putt on the 14th to claim a memorable victory.
"Luke had such an unbelievable year last year, winning both money list titles. I knew I had to play well and I did," Els said.
Donald was at a loss to explain his poor round, telling reporters: "Not sure where to start - I just didn't play well. It's disappointing. I've worked hard and to lose control of the ball is frustrating.
"I felt pretty good about where I was and I'm not sure what happened. Hopefully just one of those bad days."
2010 winner Ian Poulter is also out after he was ousting 4&3 by South Korean Bae Sang-moon, but most of the big names progressed to Thursday's second round, although Tiger Woods had to come from behind to beat Gonzolo Fernandez-Castano.
It proved to be an up and down day for Woods as he lost the first two holes to the Spaniard before hitting back to lead by one heading for the ninth.
However, after losing the 10th and 11th he recovered and by taking the 15th and 16th he ensured it would go down to the 18th. Left with an eight-foot putt for the victory, the former world number one held his nerve to send Fernandez-Castano crashing out.
Rory McIlroy can end the week as the world number one if he wins at Dove Mountain and the Northern Irishman remains in the hunt for the top prize following his win over South African George Coetzee.
It was not all plain sailing for McIlroy as he had to survive a late wobble before his 2up victory to leave him as Ireland’s sole representative in the competition as both Graeme McDowell and Darren Clarke crashed out.
McIlroy was trailing Coetzee after the ninth but he won the 11th and 12th to take the lead and he maintained his lead over the closing holes to book his place in the second round.
"Obviously it's another incentive knowing that if you win, at the end of the week you could be world number one," McIlroy.
"It's just nice to get through. That stretch (on the back nine) where I won four in a row felt like I played some good golf. I'll need to play more of that tomorrow against Anders."
McDowell managed to sink six birdies but he still lost 2&1 to YE Yang, while Clarke lost 5&4 to Nick Watney.
Lee Westwood, who can also end the week as the world number one, will face Robert Karlsson on Thursday looking to reach the third round for the first time and he knows he will have to maintain his concentration after beating Nicolas Colsaerts 3&1.
"You can't cruise your way into the tournament, as I do in a lot of them."
Elsewhere Dustin Johnston needed 20 holes to beat Jim Furyk, while Hunter Mahan dumped out Zach Johnson on the 19th hole.
Second Round Draw
Bobby Jones Bracket
(64) Ernie Els v (33) Peter Hanson
(49) Kyle Stanley v (17) Brandt Snedeker
(57) Robert Rock v (40) Mark Wilson
(9) Dustin Johnson v (41) Francesco Molinari
Ben Hogan Bracket
(4) Martin Kaymer v (29) David Toms
(13) Matt Kuchar v (20) Bubba Watson
(5) Steve Stricker v (28) Louis Oosthuizen
(53) YE Yang v (21) Hunter Mahan
Gary Player Bracket
(2) Rory McIlroy v (34) Anders Hansen
(50) Miguel Angel Jimenez v (18) Keegan Bradley
(7) Jason Day v (39) John Senden
(10) Charl Schwartzel v (42) Bae Sang-moon
Sam Snead Bracket
(3) Lee Westwood v (30) Robert Karlsson
(14) Nick Watney v (19) Tiger Woods
(59) Matteo Manassero v (38) Martin Laird
(54) Ryo Ishikawa v (43) Paul Lawrie