In the aftermath of their record 145-point defeat to Hawthorn, the Saints are counting the cost of injuries to Geary and ruckman Tom Hickey, who will miss up to 10 weeks with a foot problem.
Veteran defender Sam Fisher also seems certain to be sidelined again after experiencing hamstring tightness in the VFL on Sunday.
Geary will have surgery this week after suffering the injury to his right elbow in a contest with Hawks backman Josh Gibson early in Saturday's game – Geary's 100th – at the MCG.
St Kilda's head of football Chris Pelchen said: "Jarryn has been a key onfield leader for the Saints in 2014 and his absence will be sorely missed but we look forward to his return later this year."
Also in the Saints' swelling casualty ward are David Armitage (leg), Nathan Wright (leg), Sam Gilbert (foot), and Eli Templeton (arm), all who will be unavailable for extended periods.
