San Francisco - Defending champion Jason Day, world No 3 Henrik Stenson and last start winner and world No 6 Justin Rose were all early losers at the WGC Match Play Championship on Wednesday.
The only saving grace for the trio is the new format at TPC Harding Park means they have not been eliminated as they would have been in the past and can still progress to the weekend, although the odds are stacked against them.
Day, the seventh seed from Australia, was humbled by 56th seed Charley Hoffman 4&3 after the American won four straight holes from the 12th on, three with birdies, to close the World Golf Championships (WGC) match.
Stenson had a four-foot par putt on the 17th to dispatch Australian 60th seed John Senden but the Swede missed, allowing Senden to birdie the 18th and then the first extra hole to steal the match in 19 holes.
England's Rose was slow out of the gates and never recovered with Australian 56th seed Marc Leishman winning 3&2.
The news was better for Masters champion and world No 2 Jordan Spieth who won 4&2 against Finland's Mikko Ilonen, and world No 4 Bubba Watson who enjoyed an easy 5&4 win over Miguel Angel Jimenez of Spain.
"It's good to get off to a good start. I played solid golf today," Spieth said.
"It got a little interesting there on the back nine but a big turnaround on 12 and 13 to get 3-up and close it out on 16. I'm extremely pleased."
World No 5 Jim Furyk also prevailed 3&2 in a battle with South African George Coetzee.
Other upsets came from 50th seed Gary Woodland, who beat fellow-American 11th seed Jimmy Walker in 19 holes; 61st seed Ben Martin, who rode a hole-in-one on the 17th hole to a 1-up win over 14th seed Matt Kuchar, and Webb Simpson, the 46th seed, who beat match play specialist and 27th seed Ian Poulter 3&2.
World No 1 Rory McIlroy holds an early 1-up lead through six holes over Jason Dufner.First round scores from WGC-Championship Match Play here Wednesday (USA unless stated):
Rory McIlroy (NIR) bt Jason Dufner 5&4
Billy Horschel bt Brandt Snedeker 5&4
Jordan Spieth bt Mikko Ilonen (FIN) 4&2
Lee Westwood (ENG) bt Matt Every 1 up
John Senden (AUS) bt Henrik Stenson (SWE) 19 holes
Bill Haas bt Brendon Todd 3&2
Bubba Watson bt Miguel Angel Jimenez (ESP) 5&4
Louis Oosthuizen (RSA) bt Keegan Bradley 6&5
Jim Furyk bt George Coetzee (RSA) 3&2
Martin Kaymer (GER) bt Thongchai Jaidee (THA) 3&1
Mark Leishman (AUS) bt Justin Rose (ENG) 3&2
Anirban Lahiri (IND) bt Ryan Palmer 4&2
Charley Hoffman bt Jason Day (AUS) 4&3
Zach Johnson bt Branden Grace (RSA) 2 up
Dustin Johnson bt Matt Jones (AUS) 3&1
Charl Schwartzel (RSA) bt Victor Dubuisson (FRA) 5&4
Francesco Molinari (ITA) bt Adam Scott (AUS) 5&4
Paul Casey (ENG) bt Chris Kirk 22 holes
Sergio Garcia (ESP) bt Tommy Fleetwood (ENG) 2 up
Jamie Donaldson (WAL) bt Bernd Wiesberger (AUT) 1 up
Gary Woodland bt Jimmy Walker 19 holes
Webb Simpson bt Ian Poulter (ENG) 3&2
Marc Warren (SCO) bt JB Holmes 2&1
Brooks Koepka bt Russell Henley 1 up
Rickie Fowler bt Harris English 1 up
Shane Lowry (IRL) bt Graeme McDowell (NIR) 1 up
Ben Martin bt Matt Kuchar 1 up
Hunter Mahan bt Stephen Gallacher (SCO) 7&6
Patrick Reed bt Andy Sullivan (ENG) 2&1
Danny Willett (ENG) bt Ryan Moore 3&2
Hideki Matsuyama (JPN) bt Alexander Levy (FRA) 5&4
Joost Luiten (NED) bt Kevin Na 19 holes