Wallabies' Petaia could miss Wales Tests after shoulder injury
Petaia did the damage during an attempted tackle on Timoci Tavatavanawai in last weekend's dominant 31-0 home win over the Otago Highlanders.
He is expected to undergo surgery, facing a race to be fit for the first Test against Wales in Sydney on July 6.
Reds coach Les Kiss said Petaia was mapping out a plan with specialists.
"Obviously disappointed but he's gone and spoken with the specialists, talking through the next layer and getting that done," he said late Tuesday.
"Once he's got a pathway he can move forward and go from there.
"It's a blow without a doubt, a player of his calibre, the types of game he brings for us, his physical size, his power," added Kiss.
Petaia's absence further depletes a Reds squad already without fellow Wallabies Fraser McReight and Tate McDermott, who are serving bans for red cards, while lock Seru Uru is injured.
The Reds, who are sixth in the 12-team Super Rugby table midway through the season, host the second-placed Auckland Blues on Saturday.