PORT Adelaide's defence has taken a hit with skipper Tom Jonas ruled out due to health and safety protocols ahead of the club's clash with North Melbourne at Blundstone Arena on Saturday afternoon.

The Power had already lost Riley Bonner with an ankle injury and Jonas' withdrawal will give Ken Hinkley a challenge in the back half, especially with Nick Larkey returning from suspension for the Roos.

Running defender Martin Frederick comes into the side for his second game of the season, while Miles Bergman has been added to the emergencies.

MEDICAL ROOM Check out the full injury list

This will be the first game Jonas has missed since round nine, 2019, breaking a run of 64 consecutive appearances.

Port is looking to make it four wins in a row after a 0-5 start to the season, and will enter the game in Hobart full of momentum.

The Power has won seven of the last eight contests against the Roos but has only faced them once in the Apple Isle, North Melbourne winning that match in 2013 - Ken Hinkley's first year as senior coach.