DUAL All-Australian Zak Butters is set for a stint on the sidelines after scans showed bone bruising in his knee.

While a timeline for the midfielder's return from injury is not yet known, Port Adelaide has confirmed Butters will miss the start of the season. 

The 24-year-old suffered a heavy knock to his knee during the week, and is set to undergo a knee arthroscopy during the week to look at the surface of the joint and determine the extent of the injury.

A clearer picture of Butters' return to play timeline is expected after this procedure.

It's another injury blow for Port Adelaide, who already has a lengthy injury list heading into the season.

Forward Todd Marshall is set to miss at least half the season with an Achilles injury, while defender Brandon Zerk-Thatcher is expected to miss the start of the AFL season with a back issue. Esava Ratugolea is also no guarantee to return from knee surgery in time for round one's clash with Collingwood.