PORT Adelaide key defender Tom Jonas will be sidelined for at least a month with a knee injury.

Jonas suffered the injury during last Saturday night’s win over St Kilda and will be sidelined for 4-6 weeks.

He will undergo an arthroscopy in the next day to remove a floating loose body from his knee joint.

The 27-year-old has been in outstanding form this season and is in All Australian contention.

The Power have the luxury of calling on Jack Hombsch, who was impressive in the SANFL on Sunday, to replace Jonas for Sunday’s game with Fremantle at Optus Stadium.

Former Gold Coast defender Trent McKenzie and mature-aged rookie Jarrod Lienert are also at coach Ken Hinkley's disposal, while running defender Jasper Pittard could return from a hamstring injury to face the Dockers.

While admitting losing Jonas was a blow, key forward Charlie Dixon was confident the Power had the players to fill his role.

"He is enormous, but he's been in and out the last couple of weeks, so it might do him some good to rest the rest of the body up," Dixon said.

"We've got some really good depth at the moment. Hombschy's been great every time he's come back, we've got Trent, who came back in the (Magpies) yesterday as well.

"We've got plenty of depth there and plenty of boys we can rotate through there."

Small forward Sam Gray will be assessed this week to see if he can return from an ankle injury that forced him to miss the win over the Saints.

The Power are hopeful Matthew Broadbent's ankle injury isn't serious.

The defender rolled his left ankle in the club's SANFL game on Sunday – his second game back after two surgeries to his right ankle.

Pressure forward Jake Neade will also have a knee injury assessed.