The 23-year-old Queenslander faced up to the news on Monday after rupturing his ACL against the Western Bulldogs on Saturday night.
He played on after 'tweaking' the knee, not thinking it was too bad, but scans revealed the worst.
"(I'm) still feeling a bit disappointed," Smith told Suns TV.
"Better than I was when I found out for the first time. It was pretty emotional when the doc came into the room and told me I'd done my ACL and I'd be out for 12 months.
"That hit home. It's a lot to deal with. It's pretty big news when you're told you're not going to be playing the game you love for 12 months."
Smith has played all eight of the Suns matches this year, forming an emerging ruck combination with Charlie Dixon (ankle) who is also injured.
Assistant coach Matthew Primus has undergone three reconstructions and was one of the first to get in touch with Smith.
"He told me 'It's going to be OK and you're going to get back to where you were and your knee's going to be as strong as ever'," Smith said.
"It's good having guys like him around the club who have been through this. It gives you hope."
Coach Guy McKenna said the reality had sunk in they would be without Smith for the rest of the season.
"I think we understand what we're missing.
"Charlie Dixon, Tom Lynch, Steven May and Sam Day … they'll understand what we're missing because of his ability to do most of the ruck work and allow our tall forward structure to stay put.
"With Zac going down we have to find a replacement for him and use one of our tall forwards (as back-up), which I don't like to do because it takes away our ability when we get it in our forward 50."
McKenna said Tom Nicholls was likely to get first crack as Smith's replacement.
Michael Whiting covers Gold Coast news for AFL.com.au. Follow him on Twitter: @AFL_mikewhiting
