Jason Day laughed and joked in the interview room Tuesday morning, looking every bit like a man ready to defend his title at Austin Country Club.

The former No. 1 golfer in the world looked loose, but sounded very confident heading into this week’s World Golf Championships—Dell Technologies Match Play.

But Day took a double-bogey on the par-five sixth hole in his first match against Pat Perez on Wednesday. Perhaps the back injury that has plagued Day in the latter half of his career flared up again.

It was something much more serious than an ailment, however, that had Day’s back against the wall.

“My back is fine,” Day said. “I’m a hundred percent healthy. Everything is totally fine.”

Tears in his eyes, Day didn‘t sound nor look like a man who was doing “fine.” With good reason.

After conceding his match to Perez 3-down through six holes, Day told reporters that his mother has lung cancer. At the beginning of the year, doctors told her that she only has 12 months to live, according to Jason.

“She’s going in for surgery this Friday and it’s really hard to even comprehend being on the golf course right now because of what she’s gone through,” Day said. “It’s been very, very emotional, as you can tell.”

Day’s father, Alvin Day, died when Jason was just 12. He’s gone through it before, but not as a high-profile golfer. He said it’s been hard to play with such a serious issue on his mind — so he won’t continue to try for the time being.

Day, who said family is always first, said he is stepping away from golf indefinitely to be with his terminally ill mother.

“I’m going to try my best and try to be there the best I can for her because she is the reason that I’m playing golf today,” Day said.