However, key forward James Podsiadly and midfielder Shannon Byrnes definitely won't play.
Chapman has been battling a groin problem, while Ling suffered two hamstring strains during the summer, and neither has played in any NAB Cup or NAB Challenge matches during the pre-season.
But Scott insisted they remained a chance to take on the Saints.
"There's a big group of players - Chapman, Ling and a few other younger guys on the fringe - that we're just not sure about," Scott said at Skilled Stadium on Tuesday before a closed training session.
"We're going to train today and we certainly haven't ruled those guys out. We'll just have to make a call later in the week.
"The preparation that almost all of them has had has been pretty good. If it hadn't been so good we'd be more inclined to say 'they're just not ready to play'."
One of Geelong's most damaging players, whether in the midfield or up forward, Chapman is regarded as more likely to run out on Friday than the skipper.
"Their preparation has been different and I don't really like to compare them," Scott said.
"Paul had a really good preparation up until Christmas and has had a couple of hiccups since then.
"Paul also has a lot of flexibility in his game, so that's something we have to consider.
"[Ling's] four-week hamstring has turned into a seven-week hamstring. He's been really good in the last couple of weeks, and he trains with such intensity that you've got to think he's a chance to get up."
There is some chance that either or both Ling and Chapman will play in the Cats' VFL team against North Ballarat on Saturday.
"If we decide that they're not up to AFL intensity but they can play some footy, then the VFL is a very real option for us," Scott stated.
Podsiadly is still battling the broken hand he suffered in the opening round of the NAB Cup.
"We're really hopeful that he'll be ok for round two," said Scott, whose team meets Fremantle at Patersons Stadium in its second home and away game.
"His physical preparation in terms of the running he's been able to do has been ok.
"Virtually everything bar the ball handling has been first-class. So round two is more likely for him."
Byrnes is struggling to overcome a lower leg problem.
"Shannon's in the same situation as Podsy," Scott explained. "He's not available this week. It's only a minor injury but he does have some joint issues."
Given the injury concerns surrounding many of the Cats' veterans, a number of youngsters are set to be selected in the team to take on St Kilda.
Highly-rated forward Mitch Brown, who has suffered a broken leg and a shoulder reconstruction in the past two seasons, is among them.
"Taylor Hunt, Dan Menzel and Mitch Duncan would all be in the squad," Scott added.
"It certainly hasn't been decided whether they're in the 21 or 22 yet. We also expect [Steven] Motlop and [Nathan] Vardy to play some senior footy in the first half of the year."
Cameron Ling is $344,200 midfielder in the Toyota AFL Dream Team competition
Paul Chapman is a $472,200 midfielder/forward in the Toyota AFL Dream Team competition
