Port Adelaide will be without defender Riley Bonner after the defender was forced to follow the AFL's heath and safety protocols, while North Melbourne have confirmed two players will be unavailable for selection for this weekend for similar reasons.

Bonner will miss Saturday's clash with Collingwood due to COVID, becoming the latest Power player to be placed in isolation and miss minutes.

Port Adelaide coach Ken Hinkley confirmed the news to media on Thursday, with the Power coach to also be without backman Dan Houston due to concussion protocols for this week.

"We have a reasonably healthy squad outside of Bonner and Houston," Hinkley said, via Port Adelaide's socials.

"Everything's on the table for us. We'll see what happens at today's training and from there will work through exactly what the squad looks like for Saturday."

The Alberton club aren't the only side battling with COVID ahead of Round 20, with North Melbourne confirming earlier this week that a quartet of players have been placed in health and safety protocols, along with caretaker coach Leigh Adams.

ADELAIDE, AUSTRALIA - APRIL 21: Lachie Fogarty of the Cats tackles Riley Bonner of Port Adelaide during the round five AFL match between the Port Adelaide Power and the Geelong Cats at Adelaide Oval on April 21, 2018 in Adelaide, Australia. (Photo by Mark Brake/Getty Images)

Young pair Callum Coleman-Jones and Paul Curtis were reported to be among the unlucky Roos four, with the latter now confirmed to miss Sunday's matchup with Essendon at Marvel Stadium.

Veteran Ben Cunnington will also be unavailable for selection to due COVID protocols, while the Roos remain optimistic tall forward Nick Larkey will overcome a niggling heel injury.

Midfielder Tarryn Thomas has returned to the club following an absence due to personal reasons and could come into Adams' side, which will lose Flynn Perez to suspension for one game.

The Roos will clash with Essendon at Marvel Stadium on Sunday at 4:40pm (AEST).