AUSTIN, Texas — Jason Day was 3-up with four holes to play, an ideal start that included five birdies and hardly any stress Wednesday at the World Golf Championships Match Play.
Then he felt his back tighten on a tee shot on No. 15.
It stung so badly on his next tee shot that Day, coming off Sunday's win in the Arnold Palmer Invitational at Bay Hill, grabbed his back and winced. He stepped gingerly into a bunker. When his short par was conceded, he took a knee. Exactly what happened was not entirely clear because Day immediately sought treatment and left without speaking. But with a long week ahead of him at Austin Country Club, and the Masters just two weeks away, this victory surely felt hollow.
Jordan Spieth, a crowd favorite who helped Texas to a national title in 2012, produced what the crowd came to see. The world's No. 1 player built an early lead and en route to a 3 and 2 victory over Jamie Donaldson.
Rory McIlroy escaped with a victory. He never led until winning on the 18th hole when Thorbjorn Olesen shanked a chip. Martin Kaymer rode the wind and drove the green on the 376-yard 18th hole to wrap up a 1-up victory over Shane Lowry. Matt Kuchar had the shortest day, dispatching Anirban Lahiri in 13 holes.
Day overcame an early deficit and had the match in hand when he first felt pain. Day's agent later sent a statement that he tweaked his back, had some work done on it, was pleased with winning and is getting prepared to play today.
Day told the Australian Associated Press before getting treatment: "It's really hard to play with searing pain in both sides of your lower back. Just my back has seized up and I need to get inside right away for treatment and see what's wrong."
Day's career has been filled with injuries. He withdrew after one round in the 2012 Masters with an ankle injury. A wrist and thumb injury kept him out for much of the spring in 2014 after he won the Match Play. He suffered vertigo symptoms at the U.S. Open last year. He took three months off at the end of last year to be with his wife when she gave birth to their second child and to concentrate on his health.
There was no need to worry about Spieth, the Texas native.
"I felt like everybody was on our side today," Spieth said. "I almost felt like a home Ryder Cup match. And Jamie, I'm not sure what he would say about it. … Everyone was very respectful, but every single step I took, somebody was yelling at you, 'Hook 'em Horns' or 'Go Jordan, we're rooting for you,' which is really, really cool."
No. 5 seed Rickie Fowler rallied from 3-down to square his match on the 15th hole, only for Jason Dufner to win the next two with birdies to beat him on the 17th hole. He was the highest-ranked played to lose.
Dustin Johnson (No. 8) lost to Robert Streb, and Hideki Matsuyama (No. 12) lost to Rafa Cabrera-Bello. Adam Scott (No. 6), who has lost seven straight matches in this event, had to settle for a halve with Thomas Pieters. In the round-robin format, all of the players still have a chance to advance from their groups and reach the knockout stage. It might be easier this year because there are halves during group play. Bubba Watson (No. 4) was among six players whose matches ended in a draw.