The Giants had been hopeful vice-captain Kelly would make his comeback in the second half of the season after the 31-year-old underwent hip surgery in November.
Kelly had the operation for a recurrent right hip issue, with the club describing the surgery as "unprecedented". It required "some prosthesis components", but not a hip replacement.
With eight home-and-away rounds remaining, Kelly - in the penultimate year of his contract - has yet to start running again.
Kelly is just one of 15 injured GWS players, with highly rated ruck Nick Madden nearing his AFL return from a knee injury.
The Giants have fended off interstate rivals to retain the in-demand youngster Madden on a four-year deal.
Madden had displaced Kieren Briggs as Kingsley's preferred ruck before hurting his knee in round seven, and his new contract could have implications for off-contract Briggs.
Richmond had targeted Madden as a successor for captain Toby Nankervis, and the Giants academy product's decision to stay in Sydney could start a pursuit for Briggs.
The 14th-placed Giants (6-9) are facing an uphill battle to secure a finals berth.
GWS are on a three-game losing streak with ladder-leaders Fremantle (14-1) out to continue their misery at Manuka Oval on Saturday.
Madden will make his return via the VFL, with Kingsley ruling out a late cameo from Kelly.
"He's hopefully starting to run next week," Kingsley said of Kelly.
"Starting to run again and playing within a seven-week or eight-week window, whatever, is probably not a window that he's going to be able to get back in."
Kelly was limited to just 15 appearances last season with hip and calf injuries, but played a starring role in a 19-point elimination-final loss to Hawthorn.
His injury layoff comes as the Giants face a crossroads in their attempt to keep their premiership season alive.
GWS skipper Toby Greene has yet to re-sign with the club amid speculation the proven match-winner is open to returning to Victoria.
Greene's heir apparent Tom Green is also on the radar of expansion club Tasmania, with the ball-winner - sidelined this season with an ACL injury - contracted until the end of 2027.
Inaugural Giants player Stephen Coniglio's contract also ends this season, while Kelly is tied to the club until 2029.
The Giants will look to land young key forward Max Gruzewski's signature, with off-contract Jesse Hogan yet to make a call on his future.
Both Hogan (finger) and Gruzewski are sidelined through injury, though Gruzewski had avoided surgery for a dislocated patella following last week's defeat to Hawthorn.
GWS are also looking for a new chief executive to replace inaugural boss Dave Matthews.
Amid all the noise, Kingsley is confident Kelly can get back to his best.
"If he can get back physically and he'll have a whole pre-season to be able to do that, then I don't see any reason why he couldn't return to what he's been in the past," Kingsley said.
"But again, there's a lot of water to go under the bridge before that happens."
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