San Francisco - Defending champion Jason Day, world number three Henrik Stenson and last start winner and world number six Justin Rose were all early losers at the WGC Match Play Championship.
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 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 number two Jordan Spieth who won 4&2 against Finland's Mikko Ilonen, and world number four 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 number five 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 number one Rory McIlroy held an early 1-up lead through six holes over Jason Dufner. – Reuters