Close suffered "a significant bleed" on his brain after suffering a heavy hit against Geelong in the VFL.
The Kangaroos' medical team cleared Close to go home that afternoon, but he spent that night and the next morning vomiting before contacting the club doctor, who ordered him an ambulance.
"I had a rough night and couldn't sleep. In the morning, I knew something wasn't right when I vomited again. It wasn't a good sign," Close said.
"I was taken to hospital in Horsham for a CT scan. It showed a significant bleed on my brain, which, I'll admit, did scare me."