Rory McIlroy remains on course to retain the WGC-Dell Match Play title, but semi-final opponent Jason Day is back on top of the world.
Jason Day will move back to the top of the official world golf ranking after beating Brooks Koepka to set up a mouthwatering semi-final tie against defending champion Rory McIlroy at the WGC-Dell Match Play.
By securing his place in the last four with a 3 and 2 victory over Koepka, Day – the winner of last week's Arnold Palmer Invitational – ensured he will overtake Jordan Spieth as world number one when the latest rankings are released on Monday.
Spieth was knocked out at the last-16 stage on Saturday by Louis Oosthuizen, who went on to book his place in the last four with a 2 and 1 victory over Dustin Johnson.
Yet while a clash with surprise package Rafael Cabrera-Bello awaits Oosthuizen, greater focus is set to fall on the meeting between Day and McIlroy, the latter having beaten Chris Kirk 4 and 3 to extend his winning run in this competition to 12 matches.
McIlroy was two up after four holes and then hit top form on the back nine after a lapse in form had allowed Kirk to pull level.
"I was a little annoyed ... letting Chris get back into it with a three-putt on nine, but after that I think I was four under for my next six holes and that was enough to get the job done," said McIlroy.
"I'm just really happy that I'm playing well and have made it through to tomorrow [Sunday]. To get through to the last day for the second year in a row, it feels good."
Day, who is seeking to regain the title he won in 2014, progressed in similar fashion to McIlroy, coming on strong after the turn to end the hopes of 18th seed Koepka.
Oosthuizen, meanwhile, was one down at the halfway stage of his match with Johnson, but swiftly turned things around thereafter and birdied the penultimate hole to seal victory.
Saturday's other quarter-final saw Cabrera-Bello continue his excellent week at the expense of Ryan Moore, who was behind for all but two holes.