Reece Walsh says vomiting during matches has been a problem since he was 12, and the Rugby League World Cup opener was no exception.
"I've been doing it (throwing up) since I was 12 years old," he said.
"I don't know what it is but every time I do a big run - that's why I took my mouthguard out mid-game - I knew I was going to gag."
"Once I start doing that, it's game over. I don't know if it's nerves or sports science, but if there's anyone out there that can help me, I'll pay top dollar."
The 24-year-old scored a spectacular try in Australia's 24-22 win over New Zealand on Thursday night, but was vomiting and unable to take the conversion immediately afterwards.
Walsh also explained that the pre-match haka brought him to tears. His mother is a New Zealander of Maori descent, while his Indigenous father is from a family background that connects him to Australia; Walsh was born in Southport, Queensland.
Speaking to Channel 7 after the match, he said, "It was a special one. Both teams really passionate,"
He added, "Sitting there facing the haka, it was my first time. I was pretty emotional thinking of my family, all my friends who helped me get here."
Walsh was selected at fullback by Kevin Walters ahead of James Tedesco, whom Walters said was resting after a demanding NRL season.
"I thought he was really good," Walters said, praising Walsh's try-saving tackle on Kalyn Ponga and his attacking contributions.
Walters noted Walsh's cramps and vomiting, adding, "He's not an endurance athlete. He's a power athlete" and that he had made several major efforts.