The 23-year-old developed a hot spot in his foot after the Saints' Anzac Day loss to the Brisbane Lions in Wellington.
The ruckman wasn't named for Saturday's clash with Hawthorn with former Lion Billy Longer picked in his place for just his second game for the club.
Coach Alan Richardson said before the game that Longer was now set for a lengthy opportunity at senior level, with Hickey expected to be out for 8-10 weeks.
"Billy is one of those guys who is going to need games and we've often seen when ruckmen get the opportunity through injury or retirement that they step up," Richardson told Triple M.
"Billy's going to have that now for a fairly long time unfortunately – Tommy's going to be out of it for about 8-10 weeks with his foot.
"It will be a great opportunity for him (Longer). We're going to support him really strongly but he'll have to get the job done."
However, the club is hopeful further rest will produce a different outcome for Hickey.
The Saints’ head of football Chris Pelchen told AFL.com.au the club would wait another week before putting an ultimate number on the games Hickey would miss.
"The doctors won't know the timeframe until next week," Pelchen said on Saturday.
"They will see if it improves with a week's rest so 8-10 [weeks] is a bit premature until then.
"The doctors feel it is a stress reaction that should recover with rest."
If Hickey does face a long-term layoff, Longer will have the chance to build some continuity in senior football.
The Saints have had a disappointing run with injuries lately with Sam Gilbert (foot – 9-10 weeks), Nathan Wright (leg – 10-12 weeks) and Eli Templeton (arm – 3-4 months) ruled out for extended periods in recent weeks.
Twitter: @AFL_JenPhelan
