However, thanks to a visit from the Sharks and their star player Johnson, Jason's world was turned upside down.
"He was in a really bad place. We'd never seen it before, we were just at a loss," Greg told Fox Sports Australia.
"I can still visualise it in my head like it was yesterday.
"He had his arms on the table with his head down and it just wasn't him.
"Then Cronulla turned up with Shaun Johnson."
But it was what Johnson – who Greg described as "running around like an idiot" with a sombrero during the visit – did next that made a lasting impression on Jason.
"I got quite emotional obviously," Sharon said.
"Shaun pulled us aside and I explained what was happening with our son … how he had given up a bit.
"He took his jumper off and signed it and gave it to Jason and said 'keep the fight going mate, you've got this, I'm 100 per cent behind you'.
"It made me cry how he was so there with him.
"From then on Jason was like I've got this, I'm going to beat this."
Jason said the gesture "put a smile on my face".
"That meant a lot because no one has done that for me before," Jason said.
"He helped me put a smile on my face … it gives me a lot of strength knowing Shaun will be there with me."
Johnson, who moved to the Sharks from the Warriors last year, also posted a video online apologising to the family for not being able to see Jason while he was preparing for his own wedding with netball star Kayla Cullen.
"Jason just bawled, I bawled, Greg bawled watching that video," Sharon said.
"This guy has turned around and said Jason had an impact but I don't think he realises how much of an impact he has had on Jay and our family.
"I was shocked how this little boy has inspired this grown up and yet this grown up has inspired this little boy so much as well."
Jason is now back home for the first time in nine months after recently going into remission.
Round 23 - SJ and JasonA special day for Jason who was reunited with Shaun Johnson who he met a few months back when the Sharks visited Ronald McDonald House in Randwick. It was great to see Jason and his family again and have them help us celebrate yesterday’s win with the boys
#UpUpCronulla
Posted by Cronulla Sharks on Saturday, August 24, 2019