AUSTIN, Texas (AP) -- Jason Day assured a return to the top of the world ranking Saturday when he advanced to the semifinals of the Dell Match Play. His reward is to face Rory McIlroy, who ran his unbeaten streak to 12 matches in this event and needs two more to join Tiger Woods as the only players to win in consecutive years.
"It's been a bit of an up and down week, especially emotionally," said Day, who considered withdrawing Wednesday night when his back seized up on him. "It's been quite amazing to be able to start the week, not really thinking I'm going to be able to play with what happened Wednesday, and then turn around and I'm No. 1 in the world. It's a strange feeling. I'm glad I stuck it out."
Even with local star Jordan Spieth gone after he lost Saturday morning, the Match Play has a heavyweight battle on Sunday morning. This is only the second time since the Match Play began in 1999 that the No. 2 (Day) and No. 3 (McIlroy) seeds have met in the semifinals.
Day and McIlroy were all square going to the back in their matches. Day won two of the first three holes to pull away from Brooks Koepka, closing him out on the 16th hole. McIlroy ran off four birdies in six holes for a 4-and-3 victory over Chris Kirk.
Louis Oosthuizen, who eliminated Spieth with a 4-and-2 victory in the morning, took advantage of Dustin Johnson's blunders in the quarterfinals to win, 2 and 1. Rafa Cabrera Bello of Spain also advanced to the semifinals by beating Ryan Moore, 2 and 1.
McIlroy and Day have never faced each other in match play.
"I've love to play Jason," McIlroy said. "I'd really relish it. He's playing really well at the minute, coming off a win last week. I'd be really up for it. It's a big match."
Spieth won't be around for all the excitement.
He struck the ball poorly on the range, tried to find a quick fix on the golf course and never had a chance. He made putts of 12 feet and 25 feet on the opening two holes to keep from falling behind, but couldn't keep that up.
"I didn't make it very hard on Louis today, which is unfortunate," said Spieth, who lost holes with three bogeys and a double bogey. "I was off from when I hit my first 10 shots on the range. I've had incredible control of the ball this week and of my wedges. I'm not exactly sure what happened."
Spieth led a trail of Americans to the airport. There were 11 Americans in the round of 16 at the start of the day, none at the end of it. This is the first time since 2010 that no Americans advanced to the semifinals.
Day has played the fewest holes this week - 69 holes over five rounds - helped by an ill Paul Casey pulling out after six holes on Thursday. Day and Oosthuizen are the only players left who have yet to play the 18th hole in competition.
Day squared the match against Koepka on the eighth hole, pulled ahead with a birdie on No. 10 and then hit out of the bunker to about 20 feet for an eagle that was conceded to go 2 up. Koepka never won another hole.
McIlroy's toughest work came in the morning against Zach Johnson, who battled McIlroy to the very end. McIlroy was leading 1 up when he hit wedge to 3 feet on the 18th that seemingly wrapped up the match, except that Johnson made a 20-foot birdie putt and McIlroy had to roll in his birdie to win.
Oosthuizen reached the semifinals for the first time, and Johnson helped him get there.
Johnson three-putted for bogey on No. 11 to fall behind for the first time in the match. Oosthuizen went into the water on the par-5 12th, only for Johnson to follow with a shot into the water. Oosthuizen was 1 up playing the par-3 17th when he made a 20-foot birdie putt, and Johnson missed his birdie from 6 feet that would have extended the match.
"I just wanted to go through to tomorrow and see if I can get into this final," Oosthuizen said.
Still, so much of the attention was on McIlroy vs. Day, the last two winners of this World Golf Championship.
"I've won this tournament before and know how hard it is to win," Day said.