Scans on Sunday confirmed King had suffered a significant strain to his left hamstring.
"The key forward is expected to spend approximately six weeks on the sidelines, with his return-to-play timeline to include a conditioning block," a Saints statement read.
The Saints, powered by an eight-goal third term, kicked a triple-figure tally for the fourth time this season in their 16.12 (108) to 9.15 (69) win over Carlton on Saturday night.
It squared their win-loss record at 4-4, but coach Ross Lyon's mood in the aftermath was tempered by news of King's injury hours earlier.
The 25-year-old key forward, who hasn't played at AFL level in almost two years, kicked two early goals in his second VFL game back from a calf issue.
"I was watching it, he was looking good," Lyon said.
"I did speak about it during the week; that was the risk after such a long lay-off.
"We're trying to manage that soft tissue, so he'll be disappointed, but he's overcome bigger things."
In King's ongoing absence, St Kilda continued to find plenty of avenues to goal against Carlton.
Ruck pair Rowan Marshall (three goals) and Tom De Koning (two), Mitch Owens (three), Liam Henry (three) and Cooper Sharman (two) all provided options.
The Saints have now hit triple figures in half of their eight games this season, having done so just once last year, and are scoring at an average of 96 points per game (up from 80 in 2025).
"Yeah, it's nice. We've known our scoring capacity for a while," Lyon said.
"We feel like we've got a few different gears in our offence, which is what the good AFL teams do.
"We've still got a lot of work to do and hopefully King will get on the end of some of that.
"That would look nice, but it's not seven weeks for Max King - it's the next six years."
St Kilda will finish round eight in a 'wildcard' position but face serious obstacles in the coming weeks, starting with Gold Coast in Darwin on Saturday.
Then a clash with Richmond is followed by successive encounters with current top-three sides Fremantle (away), Hawthorn and Sydney (away).
"We've got a bit in front of us. We'll find out what we're made of," Lyon said.
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