Jason Day explains that he withdrew from his first-round match to be with his mother, who was diagnosed with lung cancer several months ago. (2:30)

AUSTIN, Texas -- Jason Day completed six holes at the WGC-Dell Technologies Match Play Championship before he simply couldn't play any longer and walked off the golf course.

Speaking through tears afterward, Day explained that his mother, Dening, was diagnosed with lung cancer in Australia at the start of the year and told she had 12 months to live. He brought her to Ohio, where Day lives with his family, in the past month for more tests, hopeful that surgery would lead to a chance for a recovery.

"It's really hard to even comprehend being on the golf course right now," Jason Day said. "It's been really hard to play golf lately. It's been very, very emotional, as you can tell. I've already gone through it once with my dad. And I know how it feels."

His father, Alvin, died of stomach cancer when Day was 12.

Day said he went through a wild streak after his father died until he was sent to a golf academy, where under the teaching and mentoring of Colin Swatton he rose to be a PGA champion and reach No. 1 in the world.

His mother took out a second mortgage on the house and borrowed money from relatives to pay for his schooling. After winning the PGA Championship in 2015, Day recalled watching her cut the lawn with a knife because they couldn't afford a lawn mower and using a kettle for hot water to bathe. He once shopped for used clothes at a store where for $5 he could stuff as much as he could into a bag.

"As of now, I'm going to try to be back there with my mom for surgery and make sure everything goes right with her," Jason Day said. "Emotionally, it's been wearing on me for a while. My mom says not to let it get to me, but it really has. ... This has been very, very tough for me. I'm going to do my best and try and be there the best I can for her, because she is the reason that I'm playing golf today.

"Family is first. It's just a hard time."

Defending Match Play champion Jason Day conceded his opening-round match against Pat Perez after six holes and later withdrew from the tournament, telling reporters through tears that his mother, Dening, has lung cancer and is undergoing surgery Friday. Erich Schlegel/USA TODAY Sports

He did not take questions, leaving the press center for his car with his wife, Ellie.

Day lives near Columbus, Ohio, where he met his wife when he was on the Nationwide Tour as a teenager trying to get his PGA Tour card.

His agent, Bud Martin, said Day's mother was at The James Cancer Hospital at Ohio State. He said the prognosis is better than what she had gotten in Australia, and doctors now hope that the cancer can be managed.

"I kidded his mother a few days ago on the phone," Martin said. "I said, 'The news seems to be getting better. I want to make certain you are there during his Hall of Fame speech.' She loves it. It's important to her to support him."

Day spoke to the media before leaving to avoid any speculation about his own health. A year ago at the Match Play, he tweaked his back in the opening round and wasn't sure he would be able to continue. Instead, he won his next six matches to capture this World Golf Championships event for the second time.

He said the mass in his mother's lung was 3 to 4 centimeters. The surgery is scheduled for Friday.

"Emotionally, it's been wearing on me for a while. My mom says not to let it get to me, but it really has. ... This has been very, very tough for me. I'm going to do my best and try and be there the best I can for her, because she is the reason that I'm playing golf today."

"I'm hoping for a speedy recovery for her and we can get this behind us and she can live a long life," Day said.

Day entered the year as the world's No. 1-ranked player. He has since dropped to No. 3, with just one top-10 finish in five starts.

He was 3 down to Pat Perez before conceding his opening-round match and has since withdrawn from the tournament. His next start is expected to be at the Masters in two weeks.

Martin said the only reason Day came to Austin for the Match Play was that he felt a responsibility to the fans -- and to his mother.

"Truthfully, the most important thing in her world is him playing golf and being happy," Martin said.

Martin said Day has not spoken much about his mother and her ordeal.

"Jason is a gutty guy," Martin said. "You don't accomplish what he's accomplished on the golf course without having resilience."

The Associated Press contributed to this report.