23/03/2017 11:01 AM AEDT | Updated 23/03/2017 4:19 PM AEDT

Jason Day Withdraws From Golf Tournament, Breaks Down Over Mum's Cancer

Dening Day will undergo surgery for lung cancer this week.

Jason Day tried to do what he does for a living, but it was too much. The Aussie golfer withdrew overnight from the WGC Match Play Tournament in Austin, Texas, because of concerns over his mother's lung cancer diagnosis.

Day, 29, was the defending champion in this tournament and until recently the world number one. But his golf game has been a little below par this year as injuries affected his body, and his mother's illness had weighed on his mind.

After six holes of his opening match, Day formally quit the tournament and explained his actions in a tearful press conference that must have been really hard for him to do.

Day is especially close to his mum Dening, who raised him and his sister solo after their father Alvin died from stomach cancer when Jason was 12.

As we've written before, the young Day found a male mentor in golf coach Col Swatton, who to this day is his caddie and confidante. But his mum was always there for him in their home town of Beaudesert, Queensland, where life was tough and the family subisted on a meagre income.

"Emotionally it's been wearing on me for a while," Day said in the press conference. "She had all the tests done in Australia and the doctors said it was terminal and she only had 12 moths to live."

Day said the prognosis has since improved, but much depends on surgery this week, when doctors will remove a "3 or 4 cm mass" in his mother's lungs.

Keyur Khamar via Getty Images

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

"I've already gone through it once with my dad, I know how it feels. It hard enough to have to go through it again. As of now I'm going to be back with my mum ... and make sure everything goes well with her.

"Family's first."

Day is married to an American, Ellie, and has has two children, Dash (4) and Lucy (1). It is not known when he'll return to golf or whether he'll contest the year's first Major, The Masters, which begins on April 6.

The Days in happier times last year, after Jason won the Match Play.