AUSTIN, Texas -- Dustin Johnson had no trouble in his debut as the No. 1 seed at the Dell Technologies Match Play.
He had five birdies in his opening eight holes at Austin Country Club, and there wasn't much Webb Simpson could do but try to extend the match as long as he could. It lasted 15 holes in a 5-and-3 victory.
"Got a long way to go, but getting the first match in the books with a win is definitely a head start," said Johnson, who is trying to win his third straight tournament.
Defending champion and third-seeded Jason Day lasted only six holes before abruptly conceding his match to Pat Perez. He then wiped away tears as he revealed his mother has lung cancer. Day withdrew to be with her in Ohio for surgery on Friday.
Rory McIlroy (No. 2), the 2015 champion and a semifinalist last year, appeared to seize control against Soren Kjeldsen when he won three straight holes to take the lead, including a 410-yard drive on the par-5 12th hole and another drive over the water to the edge of the green on the 317-yard 13th hole into the wind.
Kjeldsen, crisp as ever with his short irons, ran off four straight birdies to end the match. He took a 1-up lead with a wedge in tight on the par-5 16th, and then his pitching wedge that landed inches from the cup and settled 2 feet away for a birdie on the 17th to end it. Kjeldsen was 6 under on the round.
It was the first time McIlroy had lost his opening match since 2013, when Match Play was single elimination.
"If I had played anyone else, I might have won," McIlroy said. "Overall, I can't be too disappointed. But at the same time, when standing on the 14th tee just having won three holes in a row, I thought I had him going into a tough stretch of the golf course. But he put up three birdies in a row, and you can't do anything about that."
With the Texas crowd on his side, Spieth missed a short birdie attempt that would have given him the lead on No. 5.
Two holes later, Tanihara poured in an 18-foot birdie putt and Spieth couldn't match him. And he never caught up. Spieth didn't win a hole until the 14th -- with a bogey -- and Spieth gave him the next hole when his wedge sailed over the 15th green.
Spieth and McIlroy are not done yet, though they need some help.
The best record from the 16 four-man groups advance to the knockout stage on Saturday. Ties are determined by a sudden-death playoff, and head-to-head matchups do not count.
"I obviously have to take care of my end of the bargain tomorrow," said Spieth, who next faces Yuta Ikeda.
Hideki Matsuyama (No. 4) wasn't all that happy, either. He missed a 6-foot birdie putt against Jim Furyk and had to settle for a halve. Sergio Garcia, meanwhile, was thrilled to get a halve against Shane Lowry.
The Spaniard never led on the back nine and was 1 down going to the 18th. Lowry hit driver well left into the shaggy grass of a hazard, did well to get it on the green but then three-putted for a bogey.
Justin Thomas (No. 6) fell behind for the first time in his match against Chris Wood on the 13th hole. Thomas won the next two and then closed him out on the 17th. Next up for the PGA Tour's only three-time winner this season is Kevin Na.
"I didn't know I was playing him until you just told me," Thomas said. "I guess that can tell you how I'm viewing everything this week. I'm just going to play golf."
The Associated Press contributed to this report.