Jason Day reclaims No. 1 world ranking from Jordan Spieth

AUSTIN, Texas -- The back spasms that nearly knocked Jason Day out of the WGC-Dell Match Play Championship have not been enough to keep him from reclaiming the No. 1 spot in the world.

Day will move atop the Official World Golf Ranking on Sunday regardless of how he fares on the final day at Austin Country Club after winning two matches to advance to Sunday's semifinals against Rory McIlroy.

Jordan Spieth's exit on Saturday morning set up the No. 1 scenario for Day, provided he defeated Brooks Koepka in his quarterfinal match.

"It's not so much about the No. 1 ranking that really gets me excited,'' Day said following his 3-and-2 victory over Koepka. "It's more about the journey and the process that it's taken. To get to the top of your sport takes a lot of time and dedication. It's delayed satisfaction that I'm very happy for. To get back to No. 1 in the world is fantastic.''

Day, 28, didn't figure to get to the first tee Thursday after leaving the course in distress Wednesday, suffering from back spasms that the Australian said he has endured previously. He clutched his back following a tee shot on the 16th hole that day and was fortunate the match against Graeme McDowell ended on the 16th green.

Afterward he received treatment and said Thursday that he wasn't sure until he warmed up if he would be able to go against Thongchai Jaidee, whom he defeated 5-and-3. Day then got a break when Paul Casey had to withdraw after just six holes on Friday due to illness.

"You can definitely start thinking about it, and it's a lot of golf for my back,'' said Day, who has a bulging disk. "Especially going at it, you're playing against the guy next to you, so you've got that extra little bit of adrenaline going through you, and you try to rip at it every hole. Unfortunately sometimes it gets a little tough. I focus on getting through the day.''

Day said he was a bit tight Saturday morning, as the weather was cool prior to his 3-and-2 victory over Brandt Snedeker. After a short break and treatment, he went back out against Koepka and was 1 down through 7 holes before birdies at the 8th and 10th gave him a 1-up lead. He got to 2 up with an eagle at the 12th hole and closed out the match at the 16th.

Day first got to No. 1 in the world last September after winning the BMW Championship, his fifth victory of 2015. He gave it up after just one week but got it back again for three weeks before Spieth again became No. 1 in early November, a stretch that lasted until now.

Spieth was on his way home to Dallas after losing to Louis Oosthuizen on Saturday morning and acknowledged that he might relinquish the top spot.

"To be honest, it could be a good thing for me going into the Masters,'' said Spieth, who plays again next week at the Shell Houston Open, where it is likely there will be some scenario where he can get back to No. 1.

Day can make that more difficult if he wins for the second week in a row, following his victory at the Arnold Palmer Invitational.

First he'll have to get past McIlroy, the defending champion. And that's just to reach the final.

"I expect a really tough match in the morning against Rory,'' Day said. "It seems like he is playing some good golf right now. He was No. 1 for a long time. He is a tough competitor.''