NORTH Melbourne defender Daniel Pratt will have arthroscopic surgery on his right knee on Wednesday to repair cartilage damaged in Friday night's loss to Collingwood.

The 26-year-old also sustained a small medial ligament tear in the same knee in the second-quarter incident, however, chief of football Donald McDonald was confident Pratt would still return within three weeks.

"We hope he's an outside chance of two weeks," McDonald told kangaroos.com.au.

"It really just depends on how quickly he can get up and about from the surgery. It's not major surgery or super-intrusive."

McDonald said it could only be a week until Pratt was running with an aim to train with the main group again.

"A lot of times they walk out of hospital," he said.

"But we won't take any chances with him. He's had a bit of a torrid time. He had his shoulder surgery over the pre-season and he worked really hard to get back into senior selection for that."

Pratt was a spectator at Arden Street on Tuesday but the sideline stints of small forward Matt Campbell (hamstring) and midfielder Daniel Wells (hip) could soon be over.

McDonald said the pair would be tested in the coming days with a view to push for selection for Saturday night's clash with Port Adelaide at Docklands.

"It's just a matter of what quality work they give us," he said. "We won't play either of them until we feel they're ready to go.

"They're such important players for us but we want to make sure we don't fall into the habit of rushing them back."

McDonald added that Campbell's injury, a basic hamstring tear, had been easier to treat but the players were at similar stages.

There was some initial concern that Wells' injury could worsen.

"There's nothing saying that Daniel couldn't be at the same level of preparedness that Matt is," McDonald said.

"They're basically doing the same thing this week. They completed a good hit-out on Saturday and had another good hit-out on Monday. It's just a matter of seeing how they go tomorrow (Wednesday)."

Key defender Lachie Hansen (hamstring) remains as many as five weeks away from a return and McDonald confirmed the club was mindful of the 20-year-old's injury becoming a recurrent one.

Draftee Liam Anthony, key position prospect Robbie Tarrant and half-back Jesse Smith started running last Monday but are still a week away from joining in skills sessions.

And captain Brent Harvey, who dislocated his elbow against Richmond in round five and had surgery last week, remains upbeat in his early recovery.

Despite the disappointment of losing the Syd Barker Medallist for three months, McDonald also looked to the benefits.

"We all know he's a great on-field leader and a great player but I just think this is a really good opportunity for him to work closely with the players and the staff and the coaches," he said.

"He's been very fortunate with injury [over his career] ... so he's really using this as a positive experience."