The Power announced the news on Thursday, revealing that the 26-year-old had his left ankle caught under a teammate at training earlier in the week and suffered the injury.
Despite requiring surgery, Port are confident the former Giant will be right to go for Round 1.
"Finlayson had his left ankle caught under a teammate as he was tackled and was unable to complete training. The suspected syndesmosis injury was confirmed on MRI imaging, with the need for surgery confirmed," Port said in a statement.
"The 26-year-old is expected to be available to play in the club's season opener against Brisbane on March 18."
Jez is set for surgery, however he is still expected to be available for Round 1 ⤵️
— Port Adelaide FC (@PAFC) February 2, 2023
Finlayson made the move from GWS to Alberton at the end of the 2021 season, playing 20 games in his debut season for the Power, averaging 15.3 disposals while playing predominately in the ruck.
The 26-year-old has played 86 total career games since being drafted to the Giants in the 2014 national draft.