Two of the world's top three – Rory McIlroy and Jason Day – made it through to the last eight in Austin, but Jordan Spieth was eliminated.
World number one Jordan Spieth bowed out of the WGC-Dell Match Play at the last-16 stage on Saturday as Rory McIlroy remained on course to defend his title at Austin Country Club.
Having come through the initial round-robin stage somewhat unconvincingly, McIlroy was again made to work hard as he extended his winning streak in this competition to 11 matches with a 1up victory over Open champion Zach Johnson.
A stunning approach to three feet at the 18th essentially secured McIlroy's latest triumph and a quarter-final meeting with Chris Kirk, but Spieth – who had not been behind in his previous three matches – bowed out courtesy of a 4 and 2 defeat to another major winner, South Africa's Louis Oosthuizen.
Spieth found himself two down after seven holes this time around and was unable to recover, later telling NBC: "I'm not really sure what happened. Just really an off day. I'd like my off days to be a little more consistent than they have been of late. It's frustrating when you're just so uncomfortable over the ball."
Oosthuizen's win set up a meeting with Dustin Johnson in the last eight – the latter a 3 and 2 winner over the previously impressive Patrick Reed.
In-form US PGA champion Jason Day led from the first hole in a 3 and 2 win against Brandt Snedeker, which put the Australian through to a quarter-final tie with Brooks Koepka, who edged out Matt Kuchar.
The other tie in the quarter-finals, which began almost immediately after the round-of-16 matches, featured two less-heralded players in Rafael Cabrera-Bello of Spain and Ryan Moore, respective winners against An Byeong-hun – who withdrew with an injury when four down on the 12th – and Patton Kizzire.