King, whose last senior game was round 17 two years ago, will play for the Saints' VFL side on Sunday against Gold Coast at RSEA Park.
It will be the first time he has played at any level this season.
Asked before Friday training how long King would need in the VFL, Lyon simply replied: "It could just be this week.
"He's pretty keen to play AFL football which is a great mindset, but we just needed to give him the best opportunity, really - hold back his unbridled enthusiasm.
"I've learned, with all our players, just take it one moment at a time."
The No.4 pick in the 2018 draft was most recently hobbled by a calf muscle injury, delaying his much-anticipated comeback.
He only managed 23 games across the 2023-24 seasons before suffering a pre-season knee injury.
That ended up sidelining him for all of last year as he underwent a succession of operations.
Midway through last year, the Saints admitted King's injury had "confounded" medical experts.
In late-2024, the Saints re-signed King on a massive deal that tied him to the club until the end of the 2032 season.
At his best, King is one of the Saints' most important players and he would be a crucial addition to their forward line.
'We're thrilled for Max, thrilled for our supporters ... he's an important part of our list," Lyon said.
"I'm realistic. It will take time to build into his best.
"He's available, he's rehabbed and he'll play. He's in good shape."
The Saints will host West Coast in Sunday's AFL game at Marvel Stadium, coming off two weekends in Adelaide where they beat the Power and had a one-point loss to the Crows.
That left St Kilda in early-season trouble with a 2-4 record, although Lyon noted their two wins have been on the road.
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