The opening day of the World Golf Championship-Dell Match Play saw the world's top three players, Jordan Spieth, Jason Day and Rory McIlroy, all start the tournament with victories.
The world's highest-ranked 64 players face off in 16 groups of four before a knockout stage at the weekend, and Spieth, Day and McIlroy are all in pole position to advance.
Spieth ousted Welshman Jamie Donaldson 3&2 at Austin Country Club, while Day, who won last week's Arnold Palmer Invitational, was able to get over the line 3&2 against Graeme McDowell, despite appearing to suffer with a back injury.
McIlroy, meanwhile, was two down after 13 holes against Thorbjorn Olesen, but saw the Dane bogey three of the last five holes, including a shanked chip shot on the 18th which helped McIlroy win 1 Up.
World number 58 Jason Dufner caused the biggest upset with a 2&1 win over fifth-ranked Rickie Fowler, while the largest margin of victory on day one came from Matt Kuchar, who cruised to a 6&5 win over Anirban Lahiri in Group 7.
