Chapman, who has missed the Cats' past three matches, was not part of the main training group at Simonds Stadium on Tuesday morning.
Instead, he spent the best part of an hour doing run-throughs alongside ruckman Hamish McIntosh on the outer side of the ground.
"I'm not going to say I'm very confident (that Chapman will play this week) again because I've just been saying it every week," Geelong coach Chris Scott said on Tuesday.
"We didn't think he'd miss a week. He trained the last session before the game against the Bulldogs and just didn't quite come up.
"He got through the next week fine, got to the last session and just had a little bit of an awareness again, and the same thing happened last week.
"So clearly we're not just going to roll through the same process and keep hoping for the best. There needs to be another intervention.
"Potentially, there's another course of action that we need to take, which might make him questionable for this week, but I'm just not in a position to confirm that just yet."
The club says Chapman's problem relates to a tendon close to his knee rather than his hamstring muscle, but surgery is not part of the alternative action required.
"It's clearly a more complicated issue than was first thought, but I can categorically tell you it's not a severe hamstring strain," Scott said.
"He might go through a process of strengthening that hamstring.
"It's frustrating for Paul and it's frustrating for us, but the most important thing is that we get him completely right and he's ready to play a long stretch of footy when he does come back."
Another Geelong veteran, midfielder Joel Corey, is likely to return for Saturday night's blockbuster clash with Collingwood at the MCG after a minor knee problem kept him out of last weekend's win over Essendon.
But Taylor Hunt will be sidelined for around six weeks after having surgery to fix his broken collarbone.
"We were very fortunate to have an understanding surgeon ... who performed the surgery on Mother's Day, probably before even a few of us at the club realised it was going to happen," Scott said.
"He tells us that the surgery went extremely well and the prognosis is somewhere between four to six weeks.
"He had a fracture in the clavicle and he had a plate put over that to strengthen it and help it heal a little bit quicker.
"Sometimes those guys get back within three or four weeks. We're not even going to test those boundaries."
Scott has earmarked Jackson Thurlow and Cameron Guthrie as players capable of performing the run-with role that Hunt had fulfilled so effectively until he was injured.
As for this weekend's game, the Cats are currently seven spots higher on the ladder than the Magpies and have won three more games, but Scott and his men are taking nothing for granted.
"I thought their form against Freo was very good at times," Scott said. "To be that far down against Fremantle and come back is exceptional form.
"I thought they were very, very good against Essendon at times. And, really, we make our assumptions on the opposition given their best football … so that makes them a daunting opposition."
Adam McNicol covers Geelong news for AFL.com.au. Follow him on Twitter at @AFL_AdamMcNicol
