Petterd's new deal means the young forward, who was recruited from Broadbeach on the Gold Coast, is out of reach of the AFL's 17th team for the next two years.
Garland and Rivers' new contracts are also a sign of the club's faith after the pair battled respective foot and groin injuries in recent seasons.
Petterd told melbournefc.com.au he was delighted to remain a Demon.
“I’m pretty stoked actually,” he said.
“We got the deal done at the start of this week and the manager gave me the call and I was just pumped.”
Garland, 22, said it was a relief to sign a new contract after he missed all but one game in 2009 with a foot stress fracture.
“I’m just thankful the club has showed a bit of faith in me. The other day, I found out there was an article about [former Geelong player] Matthew Egan’s injury and how he didn’t come back," he said.
“But the club was really good and they told me they’d give me as much time as I needed. I couldn’t really do much of the pre-season at all. I’m starting to feel back to normal out there at the moment, but it’s been a long process.”
Rivers, who played his 100th game in round 14, was also pleased to have recovered from his persistent groin problems.
“I’ve worked pretty hard over the past few years to get myself right and I know what to do now with my body and recovery, so that’s very important,” he said.
“I look forward to playing the rest of this year - and two full years after that - to really get this club, where it should be, up the top.”
